class Socket

Class Socket provides access to the underlying operating system socket implementations. It can be used to provide more operating system specific functionality than the protocol-specific socket classes.

The constants defined under Socket::Constants are also defined under Socket. For example, Socket::AF_INET is usable as well as Socket::Constants::AF_INET. See Socket::Constants for the list of constants.

What’s a socket?¶ ↑

Sockets are endpoints of a bidirectional communication channel. Sockets can communicate within a process, between processes on the same machine or between different machines. There are many types of socket: TCPSocket, UDPSocket or UNIXSocket for example.

Sockets have their own vocabulary:

domain: The family of protocols:

Socket::PF_INET
Socket::PF_INET6
Socket::PF_UNIX
etc.

type: The type of communications between the two endpoints, typically

Socket::SOCK_STREAM
Socket::SOCK_DGRAM.

protocol: Typically zero. This may be used to identify a variant of a protocol.

hostname: The identifier of a network interface:

a string (hostname, IPv4 or IPv6 address or broadcast which specifies a broadcast address)
a zero-length string which specifies INADDR_ANY
an integer (interpreted as binary address in host byte order).

Quick start¶ ↑

Many of the classes, such as TCPSocket, UDPSocket or UNIXSocket, ease the use of sockets comparatively to the equivalent C programming interface.

Let’s create an internet socket using the IPv4 protocol in a C-like manner:

require 'socket'

s = Socket.new Socket::AF_INET, Socket::SOCK_STREAM
s.connect Socket.pack_sockaddr_in(80, 'example.com')

You could also use the TCPSocket class:

s = TCPSocket.new 'example.com', 80

A simple server might look like this:

require 'socket'

server = TCPServer.new 2000 # Server bound to port 2000

loop do
  client = server.accept    # Wait for a client to connect
  client.puts "Hello !"
  client.puts "Time is #{Time.now}"
  client.close
end

A simple client may look like this:

require 'socket'

s = TCPSocket.new 'localhost', 2000

while line = s.gets # Read lines from socket
  puts line         # and print them
end

s.close             # close socket when done

`Exception` Handling¶ ↑

Ruby’s Socket implementation raises exceptions based on the error generated by the system dependent implementation. This is why the methods are documented in a way that isolate Unix-based system exceptions from Windows based exceptions. If more information on a particular exception is needed, please refer to the Unix manual pages or the Windows WinSock reference.

Convenience methods¶ ↑

Although the general way to create socket is Socket.new, there are several methods of socket creation for most cases.

TCP client socket: Socket.tcp, TCPSocket.open
TCP server socket: Socket.tcp_server_loop, TCPServer.open
UNIX client socket: Socket.unix, UNIXSocket.open
UNIX server socket: Socket.unix_server_loop, UNIXServer.open

Documentation by¶ ↑

Zach Dennis
Sam Roberts
Programming Ruby from The Pragmatic Bookshelf.

Much material in this documentation is taken with permission from Programming Ruby from The Pragmatic Bookshelf.

Constants

AF_INET6: IPv6 protocol family

Attributes

tcp_fast_fallback [RW]

Public Class Methods

accept_loop (*sockets) { |socket, client_addrinfo| ... }

yield socket and client address for each a connection accepted via given sockets.

The arguments are a list of sockets. The individual argument should be a socket or an array of sockets.

This method yields the block sequentially. It means that the next connection is not accepted until the block returns. So concurrent mechanism, thread for example, should be used to service multiple clients at a time.

# File ext/socket/lib/socket.rb, line 1212
def self.accept_loop(*sockets) # :yield: socket, client_addrinfo
  sockets.flatten!(1)
  if sockets.empty?
    raise ArgumentError, "no sockets"
  end
  loop {
    readable, _, _ = IO.select(sockets)
    readable.each {|r|
      sock, addr = r.accept_nonblock(exception: false)
      next if sock == :wait_readable
      yield sock, addr
    }
  }
end

getaddrinfo(nodename, servname[, family[, socktype[, protocol[, flags[, reverse_lookup]]]]]) → array

Obtains address information for nodename:servname.

Note that Addrinfo.getaddrinfo provides the same functionality in an object oriented style.

family should be an address family such as: :INET, :INET6, etc.

socktype should be a socket type such as: :STREAM, :DGRAM, :RAW, etc.

protocol should be a protocol defined in the family, and defaults to 0 for the family.

flags should be bitwise OR of Socket::AI_* constants.

Socket.getaddrinfo("www.ruby-lang.org", "http", nil, :STREAM)
#=> [["AF_INET", 80, "carbon.ruby-lang.org", "221.186.184.68", 2, 1, 6]] # PF_INET/SOCK_STREAM/IPPROTO_TCP

Socket.getaddrinfo("localhost", nil)
#=> [["AF_INET", 0, "localhost", "127.0.0.1", 2, 1, 6],  # PF_INET/SOCK_STREAM/IPPROTO_TCP
#    ["AF_INET", 0, "localhost", "127.0.0.1", 2, 2, 17], # PF_INET/SOCK_DGRAM/IPPROTO_UDP
#    ["AF_INET", 0, "localhost", "127.0.0.1", 2, 3, 0]]  # PF_INET/SOCK_RAW/IPPROTO_IP

reverse_lookup directs the form of the third element, and has to be one of below. If reverse_lookup is omitted, the default value is nil.

+true+, +:hostname+:  hostname is obtained from numeric address using reverse lookup, which may take a time.
+false+, +:numeric+:  hostname is the same as numeric address.
+nil+:              obey to the current +do_not_reverse_lookup+ flag.

If Addrinfo object is preferred, use Addrinfo.getaddrinfo.

static VALUE
sock_s_getaddrinfo(int argc, VALUE *argv, VALUE _)
{
    VALUE host, port, family, socktype, protocol, flags, ret, revlookup;
    struct addrinfo hints;
    struct rb_addrinfo *res;
    int norevlookup;

    rb_scan_args(argc, argv, "25", &host, &port, &family, &socktype, &protocol, &flags, &revlookup);

    MEMZERO(&hints, struct addrinfo, 1);
    hints.ai_family = NIL_P(family) ? PF_UNSPEC : rsock_family_arg(family);

    if (!NIL_P(socktype)) {
        hints.ai_socktype = rsock_socktype_arg(socktype);
    }
    if (!NIL_P(protocol)) {
        hints.ai_protocol = NUM2INT(protocol);
    }
    if (!NIL_P(flags)) {
        hints.ai_flags = NUM2INT(flags);
    }
    if (NIL_P(revlookup) || !rsock_revlookup_flag(revlookup, &norevlookup)) {
        norevlookup = rsock_do_not_reverse_lookup;
    }

    res = rsock_getaddrinfo(host, port, &hints, 0);

    ret = make_addrinfo(res, norevlookup);
    rb_freeaddrinfo(res);
    return ret;
}

gethostbyaddr(address_string [, address_family]) → hostent

Use Addrinfo#getnameinfo instead. This method is deprecated for the following reasons:

Uncommon address representation: 4/16-bytes binary string to represent IPv4/IPv6 address.
gethostbyaddr() may take a long time and it may block other threads. (GVL cannot be released since gethostbyname() is not thread safe.)
This method uses gethostbyname() function already removed from POSIX.

This method obtains the host information for address.

p Socket.gethostbyaddr([221,186,184,68].pack("CCCC"))
#=> ["carbon.ruby-lang.org", [], 2, "\xDD\xBA\xB8D"]

p Socket.gethostbyaddr([127,0,0,1].pack("CCCC"))
["localhost", [], 2, "\x7F\x00\x00\x01"]
p Socket.gethostbyaddr(([0]*15+[1]).pack("C"*16))
#=> ["localhost", ["ip6-localhost", "ip6-loopback"], 10,
     "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"]

static VALUE
sock_s_gethostbyaddr(int argc, VALUE *argv, VALUE _)
{
    VALUE addr, family;
    struct hostent *h;
    char **pch;
    VALUE ary, names;
    int t = AF_INET;

    rb_warn("Socket.gethostbyaddr is deprecated; use Addrinfo#getnameinfo instead.");

    rb_scan_args(argc, argv, "11", &addr, &family);
    StringValue(addr);
    if (!NIL_P(family)) {
        t = rsock_family_arg(family);
    }
#ifdef AF_INET6
    else if (RSTRING_LEN(addr) == 16) {
        t = AF_INET6;
    }
#endif
    h = gethostbyaddr(RSTRING_PTR(addr), RSTRING_SOCKLEN(addr), t);
    if (h == NULL) {
#ifdef HAVE_HSTRERROR
        extern int h_errno;
        rb_raise(rb_eSocket, "%s", (char*)hstrerror(h_errno));
#else
        rb_raise(rb_eSocket, "host not found");
#endif
    }
    ary = rb_ary_new();
    rb_ary_push(ary, rb_str_new2(h->h_name));
    names = rb_ary_new();
    rb_ary_push(ary, names);
    if (h->h_aliases != NULL) {
        for (pch = h->h_aliases; *pch; pch++) {
            rb_ary_push(names, rb_str_new2(*pch));
        }
    }
    rb_ary_push(ary, INT2NUM(h->h_addrtype));
#ifdef h_addr
    for (pch = h->h_addr_list; *pch; pch++) {
        rb_ary_push(ary, rb_str_new(*pch, h->h_length));
    }
#else
    rb_ary_push(ary, rb_str_new(h->h_addr, h->h_length));
#endif

    return ary;
}

gethostbyname(hostname) → [official_hostname, alias_hostnames, address_family, *address_list]

Use Addrinfo.getaddrinfo instead. This method is deprecated for the following reasons:

The 3rd element of the result is the address family of the first address. The address families of the rest of the addresses are not returned.
Uncommon address representation: 4/16-bytes binary string to represent IPv4/IPv6 address.
gethostbyname() may take a long time and it may block other threads. (GVL cannot be released since gethostbyname() is not thread safe.)
This method uses gethostbyname() function already removed from POSIX.

This method obtains the host information for hostname.

p Socket.gethostbyname("hal") #=> ["localhost", ["hal"], 2, "\x7F\x00\x00\x01"]

static VALUE
sock_s_gethostbyname(VALUE obj, VALUE host)
{
    rb_warn("Socket.gethostbyname is deprecated; use Addrinfo.getaddrinfo instead.");
    struct rb_addrinfo *res =
        rsock_addrinfo(host, Qnil, AF_UNSPEC, SOCK_STREAM, AI_CANONNAME);
    return rsock_make_hostent(host, res, sock_sockaddr);
}

gethostname → hostname

Returns the hostname.

p Socket.gethostname #=> "hal"

Note that it is not guaranteed to be able to convert to IP address using gethostbyname, getaddrinfo, etc. If you need local IP address, use Socket.ip_address_list.

static VALUE
sock_gethostname(VALUE obj)
{
#if defined(NI_MAXHOST)
#  define RUBY_MAX_HOST_NAME_LEN NI_MAXHOST
#elif defined(HOST_NAME_MAX)
#  define RUBY_MAX_HOST_NAME_LEN HOST_NAME_MAX
#else
#  define RUBY_MAX_HOST_NAME_LEN 1024
#endif

    long len = RUBY_MAX_HOST_NAME_LEN;
    VALUE name;

    name = rb_str_new(0, len);
    while (gethostname(RSTRING_PTR(name), len) < 0) {
        int e = errno;
        switch (e) {
          case ENAMETOOLONG:
#ifdef __linux__
          case EINVAL:
            /* glibc before version 2.1 uses EINVAL instead of ENAMETOOLONG */
#endif
            break;
          default:
            rb_syserr_fail(e, "gethostname(3)");
        }
        rb_str_modify_expand(name, len);
        len += len;
    }
    rb_str_resize(name, strlen(RSTRING_PTR(name)));
    return name;
}

getifaddrs → [ifaddr1, ...]

Returns an array of interface addresses. An element of the array is an instance of Socket::Ifaddr.

This method can be used to find multicast-enabled interfaces:

pp Socket.getifaddrs.reject {|ifaddr|
  !ifaddr.addr.ip? || (ifaddr.flags & Socket::IFF_MULTICAST == 0)
}.map {|ifaddr| [ifaddr.name, ifaddr.ifindex, ifaddr.addr] }
#=> [["eth0", 2, #<Addrinfo: 221.186.184.67>],
#    ["eth0", 2, #<Addrinfo: fe80::216:3eff:fe95:88bb%eth0>]]

Example result on GNU/Linux:

pp Socket.getifaddrs
#=> [#<Socket::Ifaddr lo UP,LOOPBACK,RUNNING,0x10000 PACKET[protocol=0 lo hatype=772 HOST hwaddr=00:00:00:00:00:00]>,
#    #<Socket::Ifaddr eth0 UP,BROADCAST,RUNNING,MULTICAST,0x10000 PACKET[protocol=0 eth0 hatype=1 HOST hwaddr=00:16:3e:95:88:bb] broadcast=PACKET[protocol=0 eth0 hatype=1 HOST hwaddr=ff:ff:ff:ff:ff:ff]>,
#    #<Socket::Ifaddr sit0 NOARP PACKET[protocol=0 sit0 hatype=776 HOST hwaddr=00:00:00:00]>,
#    #<Socket::Ifaddr lo UP,LOOPBACK,RUNNING,0x10000 127.0.0.1 netmask=255.0.0.0>,
#    #<Socket::Ifaddr eth0 UP,BROADCAST,RUNNING,MULTICAST,0x10000 221.186.184.67 netmask=255.255.255.240 broadcast=221.186.184.79>,
#    #<Socket::Ifaddr lo UP,LOOPBACK,RUNNING,0x10000 ::1 netmask=ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff>,
#    #<Socket::Ifaddr eth0 UP,BROADCAST,RUNNING,MULTICAST,0x10000 fe80::216:3eff:fe95:88bb%eth0 netmask=ffff:ffff:ffff:ffff::>]

Example result on FreeBSD:

pp Socket.getifaddrs
#=> [#<Socket::Ifaddr usbus0 UP,0x10000 LINK[usbus0]>,
#    #<Socket::Ifaddr re0 UP,BROADCAST,RUNNING,MULTICAST,0x800 LINK[re0 3a:d0:40:9a:fe:e8]>,
#    #<Socket::Ifaddr re0 UP,BROADCAST,RUNNING,MULTICAST,0x800 10.250.10.18 netmask=255.255.255.? (7 bytes for 16 bytes sockaddr_in) broadcast=10.250.10.255>,
#    #<Socket::Ifaddr re0 UP,BROADCAST,RUNNING,MULTICAST,0x800 fe80:2::38d0:40ff:fe9a:fee8 netmask=ffff:ffff:ffff:ffff::>,
#    #<Socket::Ifaddr re0 UP,BROADCAST,RUNNING,MULTICAST,0x800 2001:2e8:408:10::12 netmask=UNSPEC>,
#    #<Socket::Ifaddr plip0 POINTOPOINT,MULTICAST,0x800 LINK[plip0]>,
#    #<Socket::Ifaddr lo0 UP,LOOPBACK,RUNNING,MULTICAST LINK[lo0]>,
#    #<Socket::Ifaddr lo0 UP,LOOPBACK,RUNNING,MULTICAST ::1 netmask=ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff>,
#    #<Socket::Ifaddr lo0 UP,LOOPBACK,RUNNING,MULTICAST fe80:4::1 netmask=ffff:ffff:ffff:ffff::>,
#    #<Socket::Ifaddr lo0 UP,LOOPBACK,RUNNING,MULTICAST 127.0.0.1 netmask=255.?.?.? (5 bytes for 16 bytes sockaddr_in)>]

static VALUE
socket_s_getifaddrs(VALUE self)
{
    return rsock_getifaddrs();
}

getnameinfo(sockaddr [, flags]) → [hostname, servicename]

Obtains name information for sockaddr.

sockaddr should be one of follows.

packed sockaddr string such as Socket.sockaddr_in(80, “127.0.0.1”)
3-elements array such as [“AF_INET”, 80, “127.0.0.1”]
4-elements array such as [“AF_INET”, 80, ignored, “127.0.0.1”]

flags should be bitwise OR of Socket::NI_* constants.

Note: The last form is compatible with IPSocket#addr and IPSocket#peeraddr.

Socket.getnameinfo(Socket.sockaddr_in(80, "127.0.0.1"))       #=> ["localhost", "www"]
Socket.getnameinfo(["AF_INET", 80, "127.0.0.1"])              #=> ["localhost", "www"]
Socket.getnameinfo(["AF_INET", 80, "localhost", "127.0.0.1"]) #=> ["localhost", "www"]

If Addrinfo object is preferred, use Addrinfo#getnameinfo.

static VALUE
sock_s_getnameinfo(int argc, VALUE *argv, VALUE _)
{
    VALUE sa, af = Qnil, host = Qnil, port = Qnil, flags, tmp;
    char hbuf[1024], pbuf[1024];
    int fl;
    struct rb_addrinfo *res = NULL;
    struct addrinfo hints, *r;
    int error, saved_errno;
    union_sockaddr ss;
    struct sockaddr *sap;
    socklen_t salen;

    sa = flags = Qnil;
    rb_scan_args(argc, argv, "11", &sa, &flags);

    fl = 0;
    if (!NIL_P(flags)) {
        fl = NUM2INT(flags);
    }
    tmp = rb_check_sockaddr_string_type(sa);
    if (!NIL_P(tmp)) {
        sa = tmp;
        if (sizeof(ss) < (size_t)RSTRING_LEN(sa)) {
            rb_raise(rb_eTypeError, "sockaddr length too big");
        }
        memcpy(&ss, RSTRING_PTR(sa), RSTRING_LEN(sa));
        if (!VALIDATE_SOCKLEN(&ss.addr, RSTRING_LEN(sa))) {
            rb_raise(rb_eTypeError, "sockaddr size differs - should not happen");
        }
        sap = &ss.addr;
        salen = RSTRING_SOCKLEN(sa);
        goto call_nameinfo;
    }
    tmp = rb_check_array_type(sa);
    if (!NIL_P(tmp)) {
        sa = tmp;
        MEMZERO(&hints, struct addrinfo, 1);
        if (RARRAY_LEN(sa) == 3) {
            af = RARRAY_AREF(sa, 0);
            port = RARRAY_AREF(sa, 1);
            host = RARRAY_AREF(sa, 2);
        }
        else if (RARRAY_LEN(sa) >= 4) {
            af = RARRAY_AREF(sa, 0);
            port = RARRAY_AREF(sa, 1);
            host = RARRAY_AREF(sa, 3);
            if (NIL_P(host)) {
                host = RARRAY_AREF(sa, 2);
            }
            else {
                /*
                 * 4th element holds numeric form, don't resolve.
                 * see rsock_ipaddr().
                 */
#ifdef AI_NUMERICHOST /* AIX 4.3.3 doesn't have AI_NUMERICHOST. */
                hints.ai_flags |= AI_NUMERICHOST;
#endif
            }
        }
        else {
            rb_raise(rb_eArgError, "array size should be 3 or 4, %ld given",
                     RARRAY_LEN(sa));
        }
        hints.ai_socktype = (fl & NI_DGRAM) ? SOCK_DGRAM : SOCK_STREAM;
        /* af */
        hints.ai_family = NIL_P(af) ? PF_UNSPEC : rsock_family_arg(af);
        res = rsock_getaddrinfo(host, port, &hints, 0);
        sap = res->ai->ai_addr;
        salen = res->ai->ai_addrlen;
    }
    else {
        rb_raise(rb_eTypeError, "expecting String or Array");
    }

  call_nameinfo:
    error = rb_getnameinfo(sap, salen, hbuf, sizeof(hbuf),
                           pbuf, sizeof(pbuf), fl);
    if (error) goto error_exit_name;
    if (res) {
        for (r = res->ai->ai_next; r; r = r->ai_next) {
            char hbuf2[1024], pbuf2[1024];

            sap = r->ai_addr;
            salen = r->ai_addrlen;
            error = rb_getnameinfo(sap, salen, hbuf2, sizeof(hbuf2),
                                   pbuf2, sizeof(pbuf2), fl);
            if (error) goto error_exit_name;
            if (strcmp(hbuf, hbuf2) != 0|| strcmp(pbuf, pbuf2) != 0) {
                rb_freeaddrinfo(res);
                rb_raise(rb_eSocket, "sockaddr resolved to multiple nodename");
            }
        }
        rb_freeaddrinfo(res);
    }
    return rb_assoc_new(rb_str_new2(hbuf), rb_str_new2(pbuf));

  error_exit_name:
    saved_errno = errno;
    if (res) rb_freeaddrinfo(res);
    errno = saved_errno;
    rsock_raise_resolution_error("getnameinfo", error);

    UNREACHABLE_RETURN(Qnil);
}

getservbyname(service_name) → port_number

getservbyname(service_name, protocol_name) → port_number

Obtains the port number for service_name.

If protocol_name is not given, “tcp” is assumed.

Socket.getservbyname("smtp")          #=> 25
Socket.getservbyname("shell")         #=> 514
Socket.getservbyname("syslog", "udp") #=> 514

static VALUE
sock_s_getservbyname(int argc, VALUE *argv, VALUE _)
{
    VALUE service, proto;
    struct servent *sp;
    long port;
    const char *servicename, *protoname = "tcp";

    rb_scan_args(argc, argv, "11", &service, &proto);
    StringValue(service);
    if (!NIL_P(proto)) StringValue(proto);
    servicename = StringValueCStr(service);
    if (!NIL_P(proto)) protoname = StringValueCStr(proto);
    sp = getservbyname(servicename, protoname);
    if (sp) {
        port = ntohs(sp->s_port);
    }
    else {
        char *end;

        port = STRTOUL(servicename, &end, 0);
        if (*end != '\0') {
            rb_raise(rb_eSocket, "no such service %s/%s", servicename, protoname);
        }
    }
    return INT2FIX(port);
}

getservbyport(port [, protocol_name]) → service

Obtains the port number for port.

If protocol_name is not given, “tcp” is assumed.

Socket.getservbyport(80)         #=> "www"
Socket.getservbyport(514, "tcp") #=> "shell"
Socket.getservbyport(514, "udp") #=> "syslog"

static VALUE
sock_s_getservbyport(int argc, VALUE *argv, VALUE _)
{
    VALUE port, proto;
    struct servent *sp;
    long portnum;
    const char *protoname = "tcp";

    rb_scan_args(argc, argv, "11", &port, &proto);
    portnum = NUM2LONG(port);
    if (portnum != (uint16_t)portnum) {
        const char *s = portnum > 0 ? "big" : "small";
        rb_raise(rb_eRangeError, "integer %ld too %s to convert into `int16_t'", portnum, s);
    }
    if (!NIL_P(proto)) protoname = StringValueCStr(proto);

    sp = getservbyport((int)htons((uint16_t)portnum), protoname);
    if (!sp) {
        rb_raise(rb_eSocket, "no such service for port %d/%s", (int)portnum, protoname);
    }
    return rb_str_new2(sp->s_name);
}

ip_address_list → array

Returns local IP addresses as an array.

The array contains Addrinfo objects.

pp Socket.ip_address_list
#=> [#<Addrinfo: 127.0.0.1>,
     #<Addrinfo: 192.168.0.128>,
     #<Addrinfo: ::1>,
     ...]

static VALUE
socket_s_ip_address_list(VALUE self)
{
#if defined(HAVE_GETIFADDRS)
    struct ifaddrs *ifp = NULL;
    struct ifaddrs *p;
    int ret;
    VALUE list;

    ret = getifaddrs(&ifp);
    if (ret == -1) {
        rb_sys_fail("getifaddrs");
    }

    list = rb_ary_new();
    for (p = ifp; p; p = p->ifa_next) {
        if (p->ifa_addr != NULL && IS_IP_FAMILY(p->ifa_addr->sa_family)) {
            struct sockaddr *addr = p->ifa_addr;
#if defined(AF_INET6) && defined(__sun)
            /*
             * OpenIndiana SunOS 5.11 getifaddrs() returns IPv6 link local
             * address with sin6_scope_id == 0.
             * So fill it from the interface name (ifa_name).
             */
            struct sockaddr_in6 addr6;
            if (addr->sa_family == AF_INET6) {
                socklen_t len = (socklen_t)sizeof(struct sockaddr_in6);
                memcpy(&addr6, addr, len);
                addr = (struct sockaddr *)&addr6;
                if (IN6_IS_ADDR_LINKLOCAL(&addr6.sin6_addr) &&
                    addr6.sin6_scope_id == 0) {
                    unsigned int ifindex = if_nametoindex(p->ifa_name);
                    if (ifindex != 0) {
                        addr6.sin6_scope_id = ifindex;
                    }
                }
            }
#endif
            rb_ary_push(list, sockaddr_obj(addr, sockaddr_len(addr)));
        }
    }

    freeifaddrs(ifp);

    return list;
#elif defined(SIOCGLIFCONF) && defined(SIOCGLIFNUM)
    /* Solaris if_tcp(7P) */
    int fd = -1;
    int ret;
    struct lifnum ln;
    struct lifconf lc;
    const char *reason = NULL;
    int save_errno;
    int i;
    VALUE list = Qnil;

    lc.lifc_buf = NULL;

    fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd == -1)
        rb_sys_fail("socket(2)");

    memset(&ln, 0, sizeof(ln));
    ln.lifn_family = AF_UNSPEC;

    ret = ioctl(fd, SIOCGLIFNUM, &ln);
    if (ret == -1) {
        reason = "SIOCGLIFNUM";
        goto finish;
    }

    memset(&lc, 0, sizeof(lc));
    lc.lifc_family = AF_UNSPEC;
    lc.lifc_flags = 0;
    lc.lifc_len = sizeof(struct lifreq) * ln.lifn_count;
    lc.lifc_req = xmalloc(lc.lifc_len);

    ret = ioctl(fd, SIOCGLIFCONF, &lc);
    if (ret == -1) {
        reason = "SIOCGLIFCONF";
        goto finish;
    }

    list = rb_ary_new();
    for (i = 0; i < ln.lifn_count; i++) {
        struct lifreq *req = &lc.lifc_req[i];
        if (IS_IP_FAMILY(req->lifr_addr.ss_family)) {
            if (req->lifr_addr.ss_family == AF_INET6 &&
                IN6_IS_ADDR_LINKLOCAL(&((struct sockaddr_in6 *)(&req->lifr_addr))->sin6_addr) &&
                ((struct sockaddr_in6 *)(&req->lifr_addr))->sin6_scope_id == 0) {
                struct lifreq req2;
                memcpy(req2.lifr_name, req->lifr_name, LIFNAMSIZ);
                ret = ioctl(fd, SIOCGLIFINDEX, &req2);
                if (ret == -1) {
                    reason = "SIOCGLIFINDEX";
                    goto finish;
                }
                ((struct sockaddr_in6 *)(&req->lifr_addr))->sin6_scope_id = req2.lifr_index;
            }
            rb_ary_push(list, sockaddr_obj((struct sockaddr *)&req->lifr_addr, req->lifr_addrlen));
        }
    }

  finish:
    save_errno = errno;
    xfree(lc.lifc_req);
    if (fd != -1)
        close(fd);
    errno = save_errno;

    if (reason)
        rb_syserr_fail(save_errno, reason);
    return list;

#elif defined(SIOCGIFCONF)
    int fd = -1;
    int ret;
#define EXTRA_SPACE ((int)(sizeof(struct ifconf) + sizeof(union_sockaddr)))
    char initbuf[4096+EXTRA_SPACE];
    char *buf = initbuf;
    int bufsize;
    struct ifconf conf;
    struct ifreq *req;
    VALUE list = Qnil;
    const char *reason = NULL;
    int save_errno;

    fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (fd == -1)
        rb_sys_fail("socket(2)");

    bufsize = sizeof(initbuf);
    buf = initbuf;

  retry:
    conf.ifc_len = bufsize;
    conf.ifc_req = (struct ifreq *)buf;

    /* fprintf(stderr, "bufsize: %d\n", bufsize); */

    ret = ioctl(fd, SIOCGIFCONF, &conf);
    if (ret == -1) {
        reason = "SIOCGIFCONF";
        goto finish;
    }

    /* fprintf(stderr, "conf.ifc_len: %d\n", conf.ifc_len); */

    if (bufsize - EXTRA_SPACE < conf.ifc_len) {
        if (bufsize < conf.ifc_len) {
            /* NetBSD returns required size for all interfaces. */
            bufsize = conf.ifc_len + EXTRA_SPACE;
        }
        else {
            bufsize = bufsize << 1;
        }
        if (buf == initbuf)
            buf = NULL;
        buf = xrealloc(buf, bufsize);
        goto retry;
    }

    close(fd);
    fd = -1;

    list = rb_ary_new();
    req = conf.ifc_req;
    while ((char*)req < (char*)conf.ifc_req + conf.ifc_len) {
        struct sockaddr *addr = &req->ifr_addr;
        if (IS_IP_FAMILY(addr->sa_family)) {
            rb_ary_push(list, sockaddr_obj(addr, sockaddr_len(addr)));
        }
#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
# ifndef _SIZEOF_ADDR_IFREQ
#  define _SIZEOF_ADDR_IFREQ(r) \
          (sizeof(struct ifreq) + \
           (sizeof(struct sockaddr) < (r).ifr_addr.sa_len ? \
            (r).ifr_addr.sa_len - sizeof(struct sockaddr) : \
            0))
# endif
        req = (struct ifreq *)((char*)req + _SIZEOF_ADDR_IFREQ(*req));
#else
        req = (struct ifreq *)((char*)req + sizeof(struct ifreq));
#endif
    }

  finish:

    save_errno = errno;
    if (buf != initbuf)
        xfree(buf);
    if (fd != -1)
        close(fd);
    errno = save_errno;

    if (reason)
        rb_syserr_fail(save_errno, reason);
    return list;

#undef EXTRA_SPACE
#elif defined(_WIN32)
    typedef struct ip_adapter_unicast_address_st {
        unsigned LONG_LONG dummy0;
        struct ip_adapter_unicast_address_st *Next;
        struct {
            struct sockaddr *lpSockaddr;
            int iSockaddrLength;
        } Address;
        int dummy1;
        int dummy2;
        int dummy3;
        long dummy4;
        long dummy5;
        long dummy6;
    } ip_adapter_unicast_address_t;
    typedef struct ip_adapter_anycast_address_st {
        unsigned LONG_LONG dummy0;
        struct ip_adapter_anycast_address_st *Next;
        struct {
            struct sockaddr *lpSockaddr;
            int iSockaddrLength;
        } Address;
    } ip_adapter_anycast_address_t;
    typedef struct ip_adapter_addresses_st {
        unsigned LONG_LONG dummy0;
        struct ip_adapter_addresses_st *Next;
        void *dummy1;
        ip_adapter_unicast_address_t *FirstUnicastAddress;
        ip_adapter_anycast_address_t *FirstAnycastAddress;
        void *dummy2;
        void *dummy3;
        void *dummy4;
        void *dummy5;
        void *dummy6;
        BYTE dummy7[8];
        DWORD dummy8;
        DWORD dummy9;
        DWORD dummy10;
        DWORD IfType;
        int OperStatus;
        DWORD dummy12;
        DWORD dummy13[16];
        void *dummy14;
    } ip_adapter_addresses_t;
    typedef ULONG (WINAPI *GetAdaptersAddresses_t)(ULONG, ULONG, PVOID, ip_adapter_addresses_t *, PULONG);
    HMODULE h;
    GetAdaptersAddresses_t pGetAdaptersAddresses;
    ULONG len;
    DWORD ret;
    ip_adapter_addresses_t *adapters;
    VALUE list;

    h = LoadLibrary("iphlpapi.dll");
    if (!h)
        rb_notimplement();
    pGetAdaptersAddresses = (GetAdaptersAddresses_t)GetProcAddress(h, "GetAdaptersAddresses");
    if (!pGetAdaptersAddresses) {
        FreeLibrary(h);
        rb_notimplement();
    }

    ret = pGetAdaptersAddresses(AF_UNSPEC, 0, NULL, NULL, &len);
    if (ret != ERROR_SUCCESS && ret != ERROR_BUFFER_OVERFLOW) {
        errno = rb_w32_map_errno(ret);
        FreeLibrary(h);
        rb_sys_fail("GetAdaptersAddresses");
    }
    adapters = (ip_adapter_addresses_t *)ALLOCA_N(BYTE, len);
    ret = pGetAdaptersAddresses(AF_UNSPEC, 0, NULL, adapters, &len);
    if (ret != ERROR_SUCCESS) {
        errno = rb_w32_map_errno(ret);
        FreeLibrary(h);
        rb_sys_fail("GetAdaptersAddresses");
    }

    list = rb_ary_new();
    for (; adapters; adapters = adapters->Next) {
        ip_adapter_unicast_address_t *uni;
        ip_adapter_anycast_address_t *any;
        if (adapters->OperStatus != 1)  /* 1 means IfOperStatusUp */
            continue;
        for (uni = adapters->FirstUnicastAddress; uni; uni = uni->Next) {
#ifndef INET6
            if (uni->Address.lpSockaddr->sa_family == AF_INET)
#else
            if (IS_IP_FAMILY(uni->Address.lpSockaddr->sa_family))
#endif
                rb_ary_push(list, sockaddr_obj(uni->Address.lpSockaddr, uni->Address.iSockaddrLength));
        }
        for (any = adapters->FirstAnycastAddress; any; any = any->Next) {
#ifndef INET6
            if (any->Address.lpSockaddr->sa_family == AF_INET)
#else
            if (IS_IP_FAMILY(any->Address.lpSockaddr->sa_family))
#endif
                rb_ary_push(list, sockaddr_obj(any->Address.lpSockaddr, any->Address.iSockaddrLength));
        }
    }

    FreeLibrary(h);
    return list;
#endif
}

new(domain, socktype [, protocol]) → socket

Creates a new socket object.

domain should be a communications domain such as: :INET, :INET6, :UNIX, etc.

socktype should be a socket type such as: :STREAM, :DGRAM, :RAW, etc.

protocol is optional and should be a protocol defined in the domain. If protocol is not given, 0 is used internally.

Socket.new(:INET, :STREAM) # TCP socket
Socket.new(:INET, :DGRAM)  # UDP socket
Socket.new(:UNIX, :STREAM) # UNIX stream socket
Socket.new(:UNIX, :DGRAM)  # UNIX datagram socket

static VALUE
sock_initialize(int argc, VALUE *argv, VALUE sock)
{
    VALUE domain, type, protocol;
    int fd;
    int d, t;

    rb_scan_args(argc, argv, "21", &domain, &type, &protocol);
    if (NIL_P(protocol))
        protocol = INT2FIX(0);

    setup_domain_and_type(domain, &d, type, &t);
    fd = rsock_socket(d, t, NUM2INT(protocol));
    if (fd < 0) rb_sys_fail("socket(2)");

    return rsock_init_sock(sock, fd);
}

sockaddr_in(port, host) → sockaddr

pack_sockaddr_in(port, host) → sockaddr

Packs port and host as an AF_INET/AF_INET6 sockaddr string.

Socket.sockaddr_in(80, "127.0.0.1")
#=> "\x02\x00\x00P\x7F\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00"

Socket.sockaddr_in(80, "::1")
#=> "\n\x00\x00P\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00"

static VALUE
sock_s_pack_sockaddr_in(VALUE self, VALUE port, VALUE host)
{
    struct rb_addrinfo *res = rsock_addrinfo(host, port, AF_UNSPEC, 0, 0);
    VALUE addr = rb_str_new((char*)res->ai->ai_addr, res->ai->ai_addrlen);

    rb_freeaddrinfo(res);

    return addr;
}

sockaddr_un(path) → sockaddr

pack_sockaddr_un(path) → sockaddr

Packs path as an AF_UNIX sockaddr string.

Socket.sockaddr_un("/tmp/sock") #=> "\x01\x00/tmp/sock\x00\x00..."

static VALUE
sock_s_pack_sockaddr_un(VALUE self, VALUE path)
{
    struct sockaddr_un sockaddr;
    VALUE addr;

    StringValue(path);
    INIT_SOCKADDR_UN(&sockaddr, sizeof(struct sockaddr_un));
    if (sizeof(sockaddr.sun_path) < (size_t)RSTRING_LEN(path)) {
        rb_raise(rb_eArgError, "too long unix socket path (%"PRIuSIZE" bytes given but %"PRIuSIZE" bytes max)",
            (size_t)RSTRING_LEN(path), sizeof(sockaddr.sun_path));
    }
    memcpy(sockaddr.sun_path, RSTRING_PTR(path), RSTRING_LEN(path));
    addr = rb_str_new((char*)&sockaddr, rsock_unix_sockaddr_len(path));

    return addr;
}

pair(domain, type, protocol) → [socket1, socket2]

socketpair(domain, type, protocol) → [socket1, socket2]

Creates a pair of sockets connected each other.

domain should be a communications domain such as: :INET, :INET6, :UNIX, etc.

socktype should be a socket type such as: :STREAM, :DGRAM, :RAW, etc.

protocol should be a protocol defined in the domain, defaults to 0 for the domain.

s1, s2 = Socket.pair(:UNIX, :STREAM, 0)
s1.send "a", 0
s1.send "b", 0
s1.close
p s2.recv(10) #=> "ab"
p s2.recv(10) #=> ""
p s2.recv(10) #=> ""

s1, s2 = Socket.pair(:UNIX, :DGRAM, 0)
s1.send "a", 0
s1.send "b", 0
p s2.recv(10) #=> "a"
p s2.recv(10) #=> "b"

VALUE
rsock_sock_s_socketpair(int argc, VALUE *argv, VALUE klass)
{
    VALUE domain, type, protocol;
    int d, t, p, sp[2];
    int ret;
    VALUE s1, s2, r;

    rb_scan_args(argc, argv, "21", &domain, &type, &protocol);
    if (NIL_P(protocol))
        protocol = INT2FIX(0);

    setup_domain_and_type(domain, &d, type, &t);
    p = NUM2INT(protocol);
    ret = rsock_socketpair(d, t, p, sp);
    if (ret < 0) {
        rb_sys_fail("socketpair(2)");
    }

    s1 = rsock_init_sock(rb_obj_alloc(klass), sp[0]);
    s2 = rsock_init_sock(rb_obj_alloc(klass), sp[1]);
    r = rb_assoc_new(s1, s2);
    if (rb_block_given_p()) {
        return rb_ensure(pair_yield, r, io_close, s1);
    }
    return r;
}

sockaddr_in(port, host) → sockaddr

pack_sockaddr_in(port, host) → sockaddr

Packs port and host as an AF_INET/AF_INET6 sockaddr string.

Socket.sockaddr_in(80, "127.0.0.1")
#=> "\x02\x00\x00P\x7F\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00"

Socket.sockaddr_in(80, "::1")
#=> "\n\x00\x00P\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00"

static VALUE
sock_s_pack_sockaddr_in(VALUE self, VALUE port, VALUE host)
{
    struct rb_addrinfo *res = rsock_addrinfo(host, port, AF_UNSPEC, 0, 0);
    VALUE addr = rb_str_new((char*)res->ai->ai_addr, res->ai->ai_addrlen);

    rb_freeaddrinfo(res);

    return addr;
}

sockaddr_un(path) → sockaddr

pack_sockaddr_un(path) → sockaddr

Packs path as an AF_UNIX sockaddr string.

Socket.sockaddr_un("/tmp/sock") #=> "\x01\x00/tmp/sock\x00\x00..."

static VALUE
sock_s_pack_sockaddr_un(VALUE self, VALUE path)
{
    struct sockaddr_un sockaddr;
    VALUE addr;

    StringValue(path);
    INIT_SOCKADDR_UN(&sockaddr, sizeof(struct sockaddr_un));
    if (sizeof(sockaddr.sun_path) < (size_t)RSTRING_LEN(path)) {
        rb_raise(rb_eArgError, "too long unix socket path (%"PRIuSIZE" bytes given but %"PRIuSIZE" bytes max)",
            (size_t)RSTRING_LEN(path), sizeof(sockaddr.sun_path));
    }
    memcpy(sockaddr.sun_path, RSTRING_PTR(path), RSTRING_LEN(path));
    addr = rb_str_new((char*)&sockaddr, rsock_unix_sockaddr_len(path));

    return addr;
}

pair(domain, type, protocol) → [socket1, socket2]

socketpair(domain, type, protocol) → [socket1, socket2]

Creates a pair of sockets connected each other.

domain should be a communications domain such as: :INET, :INET6, :UNIX, etc.

socktype should be a socket type such as: :STREAM, :DGRAM, :RAW, etc.

protocol should be a protocol defined in the domain, defaults to 0 for the domain.

s1, s2 = Socket.pair(:UNIX, :STREAM, 0)
s1.send "a", 0
s1.send "b", 0
s1.close
p s2.recv(10) #=> "ab"
p s2.recv(10) #=> ""
p s2.recv(10) #=> ""

s1, s2 = Socket.pair(:UNIX, :DGRAM, 0)
s1.send "a", 0
s1.send "b", 0
p s2.recv(10) #=> "a"
p s2.recv(10) #=> "b"

VALUE
rsock_sock_s_socketpair(int argc, VALUE *argv, VALUE klass)
{
    VALUE domain, type, protocol;
    int d, t, p, sp[2];
    int ret;
    VALUE s1, s2, r;

    rb_scan_args(argc, argv, "21", &domain, &type, &protocol);
    if (NIL_P(protocol))
        protocol = INT2FIX(0);

    setup_domain_and_type(domain, &d, type, &t);
    p = NUM2INT(protocol);
    ret = rsock_socketpair(d, t, p, sp);
    if (ret < 0) {
        rb_sys_fail("socketpair(2)");
    }

    s1 = rsock_init_sock(rb_obj_alloc(klass), sp[0]);
    s2 = rsock_init_sock(rb_obj_alloc(klass), sp[1]);
    r = rb_assoc_new(s1, s2);
    if (rb_block_given_p()) {
        return rb_ensure(pair_yield, r, io_close, s1);
    }
    return r;
}

tcp(host, port, local_host=nil, local_port=nil, [opts]) {|socket| ... }

tcp(host, port, local_host=nil, local_port=nil, [opts])

creates a new socket object connected to host:port using TCP/IP.

If local_host:local_port is given, the socket is bound to it.

The optional last argument opts is options represented by a hash. opts may have following options:

:resolv_timeout: specify the timeout of hostname resolution in seconds.
:connect_timeout: specify the timeout of conncetion in seconds.
:fast_fallback: enable Happy Eyeballs Version 2 (RFC 8305) algorithm (Enabled by default).

If a block is given, the block is called with the socket. The value of the block is returned. The socket is closed when this method returns.

If no block is given, the socket is returned.

Socket.tcp("www.ruby-lang.org", 80) {|sock|
  sock.print "GET / HTTP/1.0\r\nHost: www.ruby-lang.org\r\n\r\n"
  sock.close_write
  puts sock.read
}

# File ext/socket/lib/socket.rb, line 653
def self.tcp(host, port, local_host = nil, local_port = nil, connect_timeout: nil, resolv_timeout: nil, fast_fallback: tcp_fast_fallback, &) # :yield: socket
  sock = if fast_fallback && !(host && ip_address?(host))
    tcp_with_fast_fallback(host, port, local_host, local_port, connect_timeout:, resolv_timeout:)
  else
    tcp_without_fast_fallback(host, port, local_host, local_port, connect_timeout:, resolv_timeout:)
  end

  if block_given?
    begin
      yield sock
    ensure
      sock.close
    end
  else
    sock
  end
end

tcp_server_loop (host=nil, port) { |socket, client_addrinfo| ... }

creates a TCP/IP server on port and calls the block for each connection accepted. The block is called with a socket and a client_address as an Addrinfo object.

If host is specified, it is used with port to determine the server addresses.

The socket is not closed when the block returns. So application should close it explicitly.

This method calls the block sequentially. It means that the next connection is not accepted until the block returns. So concurrent mechanism, thread for example, should be used to service multiple clients at a time.

Note that Addrinfo.getaddrinfo is used to determine the server socket addresses. When Addrinfo.getaddrinfo returns two or more addresses, IPv4 and IPv6 address for example, all of them are used. Socket.tcp_server_loop succeeds if one socket can be used at least.

# Sequential echo server.
# It services only one client at a time.
Socket.tcp_server_loop(16807) {|sock, client_addrinfo|
  begin
    IO.copy_stream(sock, sock)
  ensure
    sock.close
  end
}

# Threaded echo server
# It services multiple clients at a time.
# Note that it may accept connections too much.
Socket.tcp_server_loop(16807) {|sock, client_addrinfo|
  Thread.new {
    begin
      IO.copy_stream(sock, sock)
    ensure
      sock.close
    end
  }
}

# File ext/socket/lib/socket.rb, line 1268
def self.tcp_server_loop(host=nil, port, &b) # :yield: socket, client_addrinfo
  tcp_server_sockets(host, port) {|sockets|
    accept_loop(sockets, &b)
  }
end

tcp_server_sockets (host=nil, port) { |sockets| ... }

creates TCP/IP server sockets for host and port. host is optional.

If no block given, it returns an array of listening sockets.

If a block is given, the block is called with the sockets. The value of the block is returned. The socket is closed when this method returns.

If port is 0, actual port number is chosen dynamically. However all sockets in the result has same port number.

# tcp_server_sockets returns two sockets.
sockets = Socket.tcp_server_sockets(1296)
p sockets #=> [#<Socket:fd 3>, #<Socket:fd 4>]

# The sockets contains IPv6 and IPv4 sockets.
sockets.each {|s| p s.local_address }
#=> #<Addrinfo: [::]:1296 TCP>
#   #<Addrinfo: 0.0.0.0:1296 TCP>

# IPv6 and IPv4 socket has same port number, 53114, even if it is chosen dynamically.
sockets = Socket.tcp_server_sockets(0)
sockets.each {|s| p s.local_address }
#=> #<Addrinfo: [::]:53114 TCP>
#   #<Addrinfo: 0.0.0.0:53114 TCP>

# The block is called with the sockets.
Socket.tcp_server_sockets(0) {|sockets|
  p sockets #=> [#<Socket:fd 3>, #<Socket:fd 4>]
}

# File ext/socket/lib/socket.rb, line 1168
def self.tcp_server_sockets(host=nil, port)
  if port == 0
    sockets = tcp_server_sockets_port0(host)
  else
    last_error = nil
    sockets = []
    begin
      Addrinfo.foreach(host, port, nil, :STREAM, nil, Socket::AI_PASSIVE) {|ai|
        begin
          s = ai.listen
        rescue SystemCallError
          last_error = $!
          next
        end
        sockets << s
      }
      if sockets.empty?
        raise last_error
      end
    rescue Exception
      sockets.each(&:close)
      raise
    end
  end
  if block_given?
    begin
      yield sockets
    ensure
      sockets.each(&:close)
    end
  else
    sockets
  end
end

tcp_with_fast_fallback (host, port, local_host = nil, local_port = nil, connect_timeout: nil, resolv_timeout: nil)

# File ext/socket/lib/socket.rb, line 671
def self.tcp_with_fast_fallback(host, port, local_host = nil, local_port = nil, connect_timeout: nil, resolv_timeout: nil)
  if local_host || local_port
    local_addrinfos = Addrinfo.getaddrinfo(local_host, local_port, nil, :STREAM, timeout: resolv_timeout)
    resolving_family_names = local_addrinfos.map { |lai| ADDRESS_FAMILIES.key(lai.afamily) }.uniq
  else
    local_addrinfos = []
    resolving_family_names = ADDRESS_FAMILIES.keys
  end

  hostname_resolution_threads = []
  resolution_store = HostnameResolutionStore.new(resolving_family_names)
  connecting_sockets = {}
  is_windows_environment ||= (RUBY_PLATFORM =~ /mswin|mingw|cygwin/)

  now = current_clock_time
  resolution_delay_expires_at = nil
  connection_attempt_delay_expires_at = nil
  user_specified_connect_timeout_at = nil
  last_error = nil

  if resolving_family_names.size == 1
    family_name = resolving_family_names.first
    addrinfos = Addrinfo.getaddrinfo(host, port, family_name, :STREAM, timeout: resolv_timeout)
    resolution_store.add_resolved(family_name, addrinfos)
    hostname_resolution_result = nil
    hostname_resolution_notifier = nil
    user_specified_resolv_timeout_at = nil
  else
    hostname_resolution_result = HostnameResolutionResult.new(resolving_family_names.size)
    hostname_resolution_notifier = hostname_resolution_result.notifier

    hostname_resolution_threads.concat(
      resolving_family_names.map { |family|
        thread_args = [family, host, port, hostname_resolution_result]
        thread = Thread.new(*thread_args) { |*thread_args| resolve_hostname(*thread_args) }
        Thread.pass
        thread
      }
    )

    user_specified_resolv_timeout_at = resolv_timeout ? now + resolv_timeout : Float::INFINITY
  end

  loop do
    if resolution_store.any_addrinfos? &&
        !resolution_delay_expires_at &&
        !connection_attempt_delay_expires_at
      while (addrinfo = resolution_store.get_addrinfo)
        if local_addrinfos.any?
          local_addrinfo = local_addrinfos.find { |lai| lai.afamily == addrinfo.afamily }

          if local_addrinfo.nil? # Connecting addrinfoと同じアドレスファミリのLocal addrinfoがない
            if resolution_store.any_addrinfos?
              # Try other Addrinfo in next "while"
              next
            elsif connecting_sockets.any? || resolution_store.any_unresolved_family?
              # Exit this "while" and wait for connections to be established or hostname resolution in next loop
              # Or exit this "while" and wait for hostname resolution in next loop
              break
            else
              raise SocketError.new 'no appropriate local address'
            end
          end
        end

        begin
          if resolution_store.any_addrinfos? ||
             connecting_sockets.any? ||
             resolution_store.any_unresolved_family?
            socket = Socket.new(addrinfo.pfamily, addrinfo.socktype, addrinfo.protocol)
            socket.bind(local_addrinfo) if local_addrinfo
            result = socket.connect_nonblock(addrinfo, exception: false)
          else
            result = socket = local_addrinfo ?
              addrinfo.connect_from(local_addrinfo, timeout: connect_timeout) :
              addrinfo.connect(timeout: connect_timeout)
          end

          if result == :wait_writable
            connection_attempt_delay_expires_at = now + CONNECTION_ATTEMPT_DELAY
            if resolution_store.empty_addrinfos?
              user_specified_connect_timeout_at = connect_timeout ? now + connect_timeout : Float::INFINITY
            end

            connecting_sockets[socket] = addrinfo
            break
          else
            return socket # connection established
          end
        rescue SystemCallError => e
          socket&.close
          last_error = e

          if resolution_store.any_addrinfos?
            # Try other Addrinfo in next "while"
            next
          elsif connecting_sockets.any? || resolution_store.any_unresolved_family?
            # Exit this "while" and wait for connections to be established or hostname resolution in next loop
            # Or exit this "while" and wait for hostname resolution in next loop
            break
          else
            raise last_error
          end
        end
      end
    end

    ends_at =
      if resolution_store.any_addrinfos?
        resolution_delay_expires_at || connection_attempt_delay_expires_at
      else
        [user_specified_resolv_timeout_at, user_specified_connect_timeout_at].compact.max
      end

    hostname_resolved, writable_sockets, except_sockets = IO.select(
      hostname_resolution_notifier,
      connecting_sockets.keys,
      # Use errorfds to wait for non-blocking connect failures on Windows
      is_windows_environment ? connecting_sockets.keys : nil,
      second_to_timeout(current_clock_time, ends_at),
    )
    now = current_clock_time
    resolution_delay_expires_at = nil if expired?(now, resolution_delay_expires_at)
    connection_attempt_delay_expires_at = nil if expired?(now, connection_attempt_delay_expires_at)

    if writable_sockets&.any?
      while (writable_socket = writable_sockets.pop)
        is_connected = is_windows_environment || (
          sockopt = writable_socket.getsockopt(Socket::SOL_SOCKET, Socket::SO_ERROR)
          sockopt.int.zero?
        )

        if is_connected
          connecting_sockets.delete writable_socket
          return writable_socket
        else
          failed_ai = connecting_sockets.delete writable_socket
          writable_socket.close
          ip_address = failed_ai.ipv6? ? "[#{failed_ai.ip_address}]" : failed_ai.ip_address
          last_error = SystemCallError.new("connect(2) for #{ip_address}:#{failed_ai.ip_port}", sockopt.int)

          if writable_sockets.any? ||
             resolution_store.any_addrinfos? ||
             connecting_sockets.any? ||
             resolution_store.any_unresolved_family?
            user_specified_connect_timeout_at = nil if connecting_sockets.empty?
            # Try other writable socket in next "while"
            # Or exit this "while" and try other connection attempt
            # Or exit this "while" and wait for connections to be established or hostname resolution in next loop
            # Or exit this "while" and wait for hostname resolution in next loop
          else
            raise last_error
          end
        end
      end
    end

    if except_sockets&.any?
      except_sockets.each do |except_socket|
        failed_ai = connecting_sockets.delete except_socket
        sockopt = except_socket.getsockopt(Socket::SOL_SOCKET, Socket::SO_CONNECT_TIME)
        except_socket.close
        ip_address = failed_ai.ipv6? ? "[#{failed_ai.ip_address}]" : failed_ai.ip_address
        last_error = SystemCallError.new("connect(2) for #{ip_address}:#{failed_ai.ip_port}", sockopt.int)

        if writable_sockets.any? ||
           resolution_store.any_addrinfos? ||
           connecting_sockets.any? ||
           resolution_store.any_unresolved_family?
          user_specified_connect_timeout_at = nil if connecting_sockets.empty?
          # Try other writable socket in next "while"
          # Or exit this "while" and try other connection attempt
          # Or exit this "while" and wait for connections to be established or hostname resolution in next loop
          # Or exit this "while" and wait for hostname resolution in next loop
        else
          raise last_error
        end
      end
    end

    if hostname_resolved&.any?
      while (family_and_result = hostname_resolution_result.get)
        family_name, result = family_and_result

        if result.is_a? Exception
          resolution_store.add_error(family_name, result)

          unless (Socket.const_defined?(:EAI_ADDRFAMILY)) &&
            (result.is_a?(Socket::ResolutionError)) &&
            (result.error_code == Socket::EAI_ADDRFAMILY)
            last_error = result
          end
        else
          resolution_store.add_resolved(family_name, result)
        end
      end

      if resolution_store.resolved?(:ipv4)
        if resolution_store.resolved?(:ipv6)
          hostname_resolution_notifier = nil
          resolution_delay_expires_at = nil
          user_specified_resolv_timeout_at = nil
        elsif resolution_store.resolved_successfully?(:ipv4)
          resolution_delay_expires_at = now + RESOLUTION_DELAY
        end
      end
    end

    if resolution_store.empty_addrinfos?
      if connecting_sockets.empty? && resolution_store.resolved_all_families?
        raise last_error
      end

      if (expired?(now, user_specified_resolv_timeout_at) || resolution_store.resolved_all_families?) &&
         (expired?(now, user_specified_connect_timeout_at) || connecting_sockets.empty?)
        raise Errno::ETIMEDOUT, 'user specified timeout'
      end
    end
  end
ensure
  hostname_resolution_threads.each do |thread|
    thread.exit
  end

  hostname_resolution_result&.close

  connecting_sockets.each_key do |connecting_socket|
    connecting_socket.close
  end
end

udp_server_loop(port) {|msg, msg_src| ... }

udp_server_loop(host, port) {|msg, msg_src| ... }

creates a UDP/IP server on port and calls the block for each message arrived. The block is called with the message and its source information.

This method allocates sockets internally using port. If host is specified, it is used conjunction with port to determine the server addresses.

The msg is a string.

The msg_src is a Socket::UDPSource object. It is used for reply.

# UDP/IP echo server.
Socket.udp_server_loop(9261) {|msg, msg_src|
  msg_src.reply msg
}

# File ext/socket/lib/socket.rb, line 1438
def self.udp_server_loop(host=nil, port, &b) # :yield: message, message_source
  udp_server_sockets(host, port) {|sockets|
    udp_server_loop_on(sockets, &b)
  }
end

udp_server_loop_on(sockets) {|msg, msg_src| ... }

Run UDP/IP server loop on the given sockets.

The return value of Socket.udp_server_sockets is appropriate for the argument.

It calls the block for each message received.

# File ext/socket/lib/socket.rb, line 1411
def self.udp_server_loop_on(sockets, &b) # :yield: msg, msg_src
  loop {
    readable, _, _ = IO.select(sockets)
    udp_server_recv(readable, &b)
  }
end

udp_server_recv(sockets) {|msg, msg_src| ... }

Receive UDP/IP packets from the given sockets. For each packet received, the block is called.

The block receives msg and msg_src. msg is a string which is the payload of the received packet. msg_src is a Socket::UDPSource object which is used for reply.

Socket.udp_server_loop can be implemented using this method as follows.

udp_server_sockets(host, port) {|sockets|
  loop {
    readable, _, _ = IO.select(sockets)
    udp_server_recv(readable) {|msg, msg_src| ... }
  }
}

# File ext/socket/lib/socket.rb, line 1384
def self.udp_server_recv(sockets)
  sockets.each {|r|
    msg, sender_addrinfo, _, *controls = r.recvmsg_nonblock(exception: false)
    next if msg == :wait_readable
    ai = r.local_address
    if ai.ipv6? and pktinfo = controls.find {|c| c.cmsg_is?(:IPV6, :PKTINFO) }
      ai = Addrinfo.udp(pktinfo.ipv6_pktinfo_addr.ip_address, ai.ip_port)
      yield msg, UDPSource.new(sender_addrinfo, ai) {|reply_msg|
        r.sendmsg reply_msg, 0, sender_addrinfo, pktinfo
      }
    else
      yield msg, UDPSource.new(sender_addrinfo, ai) {|reply_msg|
        r.send reply_msg, 0, sender_addrinfo
      }
    end
  }
end

udp_server_sockets([host, ] port)

Creates UDP/IP sockets for a UDP server.

If no block given, it returns an array of sockets.

If a block is given, the block is called with the sockets. The value of the block is returned. The sockets are closed when this method returns.

If port is zero, some port is chosen. But the chosen port is used for the all sockets.

# UDP/IP echo server
Socket.udp_server_sockets(0) {|sockets|
  p sockets.first.local_address.ip_port     #=> 32963
  Socket.udp_server_loop_on(sockets) {|msg, msg_src|
    msg_src.reply msg
  }
}

# File ext/socket/lib/socket.rb, line 1296
def self.udp_server_sockets(host=nil, port)
  last_error = nil
  sockets = []

  ipv6_recvpktinfo = nil
  if defined? Socket::AncillaryData
    if defined? Socket::IPV6_RECVPKTINFO # RFC 3542
      ipv6_recvpktinfo = Socket::IPV6_RECVPKTINFO
    elsif defined? Socket::IPV6_PKTINFO # RFC 2292
      ipv6_recvpktinfo = Socket::IPV6_PKTINFO
    end
  end

  local_addrs = Socket.ip_address_list

  ip_list = []
  Addrinfo.foreach(host, port, nil, :DGRAM, nil, Socket::AI_PASSIVE) {|ai|
    if ai.ipv4? && ai.ip_address == "0.0.0.0"
      local_addrs.each {|a|
        next unless a.ipv4?
        ip_list << Addrinfo.new(a.to_sockaddr, :INET, :DGRAM, 0);
      }
    elsif ai.ipv6? && ai.ip_address == "::" && !ipv6_recvpktinfo
      local_addrs.each {|a|
        next unless a.ipv6?
        ip_list << Addrinfo.new(a.to_sockaddr, :INET6, :DGRAM, 0);
      }
    else
      ip_list << ai
    end
  }
  ip_list.uniq!(&:to_sockaddr)

  if port == 0
    sockets = ip_sockets_port0(ip_list, false)
  else
    ip_list.each {|ip|
      ai = Addrinfo.udp(ip.ip_address, port)
      begin
        s = ai.bind
      rescue SystemCallError
        last_error = $!
        next
      end
      sockets << s
    }
    if sockets.empty?
      raise last_error
    end
  end

  sockets.each {|s|
    ai = s.local_address
    if ipv6_recvpktinfo && ai.ipv6? && ai.ip_address == "::"
      s.setsockopt(:IPV6, ipv6_recvpktinfo, 1)
    end
  }

  if block_given?
    begin
      yield sockets
    ensure
      sockets.each(&:close) if sockets
    end
  else
    sockets
  end
end

unix (path) { |socket| ... }

creates a new socket connected to path using UNIX socket socket.

If a block is given, the block is called with the socket. The value of the block is returned. The socket is closed when this method returns.

If no block is given, the socket is returned.

# talk to /tmp/sock socket.
Socket.unix("/tmp/sock") {|sock|
  t = Thread.new { IO.copy_stream(sock, STDOUT) }
  IO.copy_stream(STDIN, sock)
  t.join
}

# File ext/socket/lib/socket.rb, line 1488
def self.unix(path) # :yield: socket
  addr = Addrinfo.unix(path)
  sock = addr.connect
  if block_given?
    begin
      yield sock
    ensure
      sock.close
    end
  else
    sock
  end
end

unix_server_loop (path) { |socket, client_addrinfo| ... }

creates a UNIX socket server on path. It calls the block for each socket accepted.

If host is specified, it is used with port to determine the server ports.

The socket is not closed when the block returns. So application should close it.

This method deletes the socket file pointed by path at first if the file is a socket file and it is owned by the user of the application. This is safe only if the directory of path is not changed by a malicious user. So don’t use /tmp/malicious-users-directory/socket. Note that /tmp/socket and /tmp/your-private-directory/socket is safe assuming that /tmp has sticky bit.

# Sequential echo server.
# It services only one client at a time.
Socket.unix_server_loop("/tmp/sock") {|sock, client_addrinfo|
  begin
    IO.copy_stream(sock, sock)
  ensure
    sock.close
  end
}

# File ext/socket/lib/socket.rb, line 1575
def self.unix_server_loop(path, &b) # :yield: socket, client_addrinfo
  unix_server_socket(path) {|serv|
    accept_loop(serv, &b)
  }
end

unix_server_socket (path) { |s| ... }

creates a UNIX server socket on path

If no block given, it returns a listening socket.

If a block is given, it is called with the socket and the block value is returned. When the block exits, the socket is closed and the socket file is removed.

socket = Socket.unix_server_socket("/tmp/s")
p socket                  #=> #<Socket:fd 3>
p socket.local_address    #=> #<Addrinfo: /tmp/s SOCK_STREAM>

Socket.unix_server_socket("/tmp/sock") {|s|
  p s                     #=> #<Socket:fd 3>
  p s.local_address       #=> # #<Addrinfo: /tmp/sock SOCK_STREAM>
}

# File ext/socket/lib/socket.rb, line 1518
def self.unix_server_socket(path)
  unless unix_socket_abstract_name?(path)
    begin
      st = File.lstat(path)
    rescue Errno::ENOENT
    end
    if st&.socket? && st.owned?
      File.unlink path
    end
  end
  s = Addrinfo.unix(path).listen
  if block_given?
    begin
      yield s
    ensure
      s.close
      unless unix_socket_abstract_name?(path)
        File.unlink path
      end
    end
  else
    s
  end
end

unpack_sockaddr_in(sockaddr) → [port, ip_address]

Unpacks sockaddr into port and ip_address.

sockaddr should be a string or an addrinfo for AF_INET/AF_INET6.

sockaddr = Socket.sockaddr_in(80, "127.0.0.1")
p sockaddr #=> "\x02\x00\x00P\x7F\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00"
p Socket.unpack_sockaddr_in(sockaddr) #=> [80, "127.0.0.1"]

static VALUE
sock_s_unpack_sockaddr_in(VALUE self, VALUE addr)
{
    struct sockaddr_in * sockaddr;
    VALUE host;

    sockaddr = (struct sockaddr_in*)SockAddrStringValuePtr(addr);
    if (RSTRING_LEN(addr) <
        (char*)&((struct sockaddr *)sockaddr)->sa_family +
        sizeof(((struct sockaddr *)sockaddr)->sa_family) -
        (char*)sockaddr)
        rb_raise(rb_eArgError, "too short sockaddr");
    if (((struct sockaddr *)sockaddr)->sa_family != AF_INET
#ifdef INET6
        && ((struct sockaddr *)sockaddr)->sa_family != AF_INET6
#endif
        ) {
#ifdef INET6
        rb_raise(rb_eArgError, "not an AF_INET/AF_INET6 sockaddr");
#else
        rb_raise(rb_eArgError, "not an AF_INET sockaddr");
#endif
    }
    host = rsock_make_ipaddr((struct sockaddr*)sockaddr, RSTRING_SOCKLEN(addr));
    return rb_assoc_new(INT2NUM(ntohs(sockaddr->sin_port)), host);
}

unpack_sockaddr_un(sockaddr) → path

Unpacks sockaddr into path.

sockaddr should be a string or an addrinfo for AF_UNIX.

sockaddr = Socket.sockaddr_un("/tmp/sock")
p Socket.unpack_sockaddr_un(sockaddr) #=> "/tmp/sock"

static VALUE
sock_s_unpack_sockaddr_un(VALUE self, VALUE addr)
{
    struct sockaddr_un * sockaddr;
    VALUE path;

    sockaddr = (struct sockaddr_un*)SockAddrStringValuePtr(addr);
    if (RSTRING_LEN(addr) <
        (char*)&((struct sockaddr *)sockaddr)->sa_family +
        sizeof(((struct sockaddr *)sockaddr)->sa_family) -
        (char*)sockaddr)
        rb_raise(rb_eArgError, "too short sockaddr");
    if (((struct sockaddr *)sockaddr)->sa_family != AF_UNIX) {
        rb_raise(rb_eArgError, "not an AF_UNIX sockaddr");
    }
    if (sizeof(struct sockaddr_un) < (size_t)RSTRING_LEN(addr)) {
        rb_raise(rb_eTypeError, "too long sockaddr_un - %ld longer than %d",
                 RSTRING_LEN(addr), (int)sizeof(struct sockaddr_un));
    }
    path = rsock_unixpath_str(sockaddr, RSTRING_SOCKLEN(addr));
    return path;
}

Public Instance Methods

accept → [client_socket, client_addrinfo]

Accepts a next connection. Returns a new Socket object and Addrinfo object.

serv = Socket.new(:INET, :STREAM, 0)
serv.listen(5)
c = Socket.new(:INET, :STREAM, 0)
c.connect(serv.connect_address)
p serv.accept #=> [#<Socket:fd 6>, #<Addrinfo: 127.0.0.1:48555 TCP>]

static VALUE
sock_accept(VALUE server)
{
    union_sockaddr buffer;
    socklen_t length = (socklen_t)sizeof(buffer);

    VALUE peer = rsock_s_accept(rb_cSocket, server, &buffer.addr, &length);

    return rb_assoc_new(peer, rsock_io_socket_addrinfo(peer, &buffer.addr, length));
}

accept_nonblock([options]) → [client_socket, client_addrinfo]

Accepts an incoming connection using accept(2) after O_NONBLOCK is set for the underlying file descriptor. It returns an array containing the accepted socket for the incoming connection, client_socket, and an Addrinfo, client_addrinfo.

Example¶ ↑

# In one script, start this first
require 'socket'
include Socket::Constants
socket = Socket.new(AF_INET, SOCK_STREAM, 0)
sockaddr = Socket.sockaddr_in(2200, 'localhost')
socket.bind(sockaddr)
socket.listen(5)
begin # emulate blocking accept
  client_socket, client_addrinfo = socket.accept_nonblock
rescue IO::WaitReadable, Errno::EINTR
  IO.select([socket])
  retry
end
puts "The client said, '#{client_socket.readline.chomp}'"
client_socket.puts "Hello from script one!"
socket.close

# In another script, start this second
require 'socket'
include Socket::Constants
socket = Socket.new(AF_INET, SOCK_STREAM, 0)
sockaddr = Socket.sockaddr_in(2200, 'localhost')
socket.connect(sockaddr)
socket.puts "Hello from script 2."
puts "The server said, '#{socket.readline.chomp}'"
socket.close

Refer to Socket#accept for the exceptions that may be thrown if the call to accept_nonblock fails.

Socket#accept_nonblock may raise any error corresponding to accept(2) failure, including Errno::EWOULDBLOCK.

If the exception is Errno::EWOULDBLOCK, Errno::EAGAIN, Errno::ECONNABORTED or Errno::EPROTO, it is extended by IO::WaitReadable. So IO::WaitReadable can be used to rescue the exceptions for retrying accept_nonblock.

By specifying a keyword argument exception to false, you can indicate that accept_nonblock should not raise an IO::WaitReadable exception, but return the symbol :wait_readable instead.

See¶ ↑

Socket#accept

# File ext/socket/lib/socket.rb, line 598
def accept_nonblock(exception: true)
  __accept_nonblock(exception)
end

bind(local_sockaddr) → 0

Binds to the given local address.

Parameter¶ ↑

local_sockaddr - the struct sockaddr contained in a string or an Addrinfo object

Example¶ ↑

require 'socket'

# use Addrinfo
socket = Socket.new(:INET, :STREAM, 0)
socket.bind(Addrinfo.tcp("127.0.0.1", 2222))
p socket.local_address #=> #<Addrinfo: 127.0.0.1:2222 TCP>

# use struct sockaddr
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
socket.bind( sockaddr )

Unix-based Exceptions¶ ↑

On unix-based based systems the following system exceptions may be raised if the call to bind fails:

Errno::EACCES - the specified sockaddr is protected and the current user does not have permission to bind to it
Errno::EADDRINUSE - the specified sockaddr is already in use
Errno::EADDRNOTAVAIL - the specified sockaddr is not available from the local machine
Errno::EAFNOSUPPORT - the specified sockaddr is not a valid address for the family of the calling socket
Errno::EBADF - the sockaddr specified is not a valid file descriptor
Errno::EFAULT - the sockaddr argument cannot be accessed
Errno::EINVAL - the socket is already bound to an address, and the protocol does not support binding to the new sockaddr or the socket has been shut down.
Errno::EINVAL - the address length is not a valid length for the address family
Errno::ENAMETOOLONG - the pathname resolved had a length which exceeded PATH_MAX
Errno::ENOBUFS - no buffer space is available
Errno::ENOSR - there were insufficient STREAMS resources available to complete the operation
Errno::ENOTSOCK - the socket does not refer to a socket
Errno::EOPNOTSUPP - the socket type of the socket does not support binding to an address

On unix-based based systems if the address family of the calling socket is Socket::AF_UNIX the follow exceptions may be raised if the call to bind fails:

Errno::EACCES - search permission is denied for a component of the prefix path or write access to the socket is denied
Errno::EDESTADDRREQ - the sockaddr argument is a null pointer
Errno::EISDIR - same as Errno::EDESTADDRREQ
Errno::EIO - an i/o error occurred
Errno::ELOOP - too many symbolic links were encountered in translating the pathname in sockaddr
Errno::ENAMETOOLLONG - a component of a pathname exceeded NAME_MAX characters, or an entire pathname exceeded PATH_MAX characters
Errno::ENOENT - a component of the pathname does not name an existing file or the pathname is an empty string
Errno::ENOTDIR - a component of the path prefix of the pathname in sockaddr is not a directory
Errno::EROFS - the name would reside on a read only filesystem

Windows Exceptions¶ ↑

On Windows systems the following system exceptions may be raised if the call to bind fails:

Errno::ENETDOWN– the network is down
Errno::EACCES - the attempt to connect the datagram socket to the broadcast address failed
Errno::EADDRINUSE - the socket’s local address is already in use
Errno::EADDRNOTAVAIL - the specified address is not a valid address for this computer
Errno::EFAULT - the socket’s internal address or address length parameter is too small or is not a valid part of the user space addressed
Errno::EINVAL - the socket is already bound to an address
Errno::ENOBUFS - no buffer space is available
Errno::ENOTSOCK - the socket argument does not refer to a socket

See¶ ↑

bind manual pages on unix-based systems
bind function in Microsoft’s Winsock functions reference

static VALUE
sock_bind(VALUE sock, VALUE addr)
{
    VALUE rai;
    rb_io_t *fptr;

    SockAddrStringValueWithAddrinfo(addr, rai);
    GetOpenFile(sock, fptr);
    if (bind(fptr->fd, (struct sockaddr*)RSTRING_PTR(addr), RSTRING_SOCKLEN(addr)) < 0)
        rsock_sys_fail_raddrinfo_or_sockaddr("bind(2)", addr, rai);

    return INT2FIX(0);
}

connect(remote_sockaddr) → 0

Requests a connection to be made on the given remote_sockaddr. Returns 0 if successful, otherwise an exception is raised.

Parameter¶ ↑

remote_sockaddr - the struct sockaddr contained in a string or Addrinfo object

Example:¶ ↑

# Pull down Google's web page
require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 80, 'www.google.com' )
socket.connect( sockaddr )
socket.write( "GET / HTTP/1.0\r\n\r\n" )
results = socket.read

Unix-based Exceptions¶ ↑

On unix-based systems the following system exceptions may be raised if the call to connect fails:

Errno::EACCES - search permission is denied for a component of the prefix path or write access to the socket is denied
Errno::EADDRINUSE - the sockaddr is already in use
Errno::EADDRNOTAVAIL - the specified sockaddr is not available from the local machine
Errno::EAFNOSUPPORT - the specified sockaddr is not a valid address for the address family of the specified socket
Errno::EALREADY - a connection is already in progress for the specified socket
Errno::EBADF - the socket is not a valid file descriptor
Errno::ECONNREFUSED - the target sockaddr was not listening for connections refused the connection request
Errno::ECONNRESET - the remote host reset the connection request
Errno::EFAULT - the sockaddr cannot be accessed
Errno::EHOSTUNREACH - the destination host cannot be reached (probably because the host is down or a remote router cannot reach it)
Errno::EINPROGRESS - the O_NONBLOCK is set for the socket and the connection cannot be immediately established; the connection will be established asynchronously
Errno::EINTR - the attempt to establish the connection was interrupted by delivery of a signal that was caught; the connection will be established asynchronously
Errno::EISCONN - the specified socket is already connected
Errno::EINVAL - the address length used for the sockaddr is not a valid length for the address family or there is an invalid family in sockaddr
Errno::ENAMETOOLONG - the pathname resolved had a length which exceeded PATH_MAX
Errno::ENETDOWN - the local interface used to reach the destination is down
Errno::ENETUNREACH - no route to the network is present
Errno::ENOBUFS - no buffer space is available
Errno::ENOSR - there were insufficient STREAMS resources available to complete the operation
Errno::ENOTSOCK - the socket argument does not refer to a socket
Errno::EOPNOTSUPP - the calling socket is listening and cannot be connected
Errno::EPROTOTYPE - the sockaddr has a different type than the socket bound to the specified peer address
Errno::ETIMEDOUT - the attempt to connect timed out before a connection was made.

On unix-based systems if the address family of the calling socket is AF_UNIX the follow exceptions may be raised if the call to connect fails:

Errno::EIO - an i/o error occurred while reading from or writing to the file system
Errno::ELOOP - too many symbolic links were encountered in translating the pathname in sockaddr
Errno::ENAMETOOLLONG - a component of a pathname exceeded NAME_MAX characters, or an entire pathname exceeded PATH_MAX characters
Errno::ENOENT - a component of the pathname does not name an existing file or the pathname is an empty string
Errno::ENOTDIR - a component of the path prefix of the pathname in sockaddr is not a directory

Windows Exceptions¶ ↑

On Windows systems the following system exceptions may be raised if the call to connect fails:

Errno::ENETDOWN - the network is down
Errno::EADDRINUSE - the socket’s local address is already in use
Errno::EINTR - the socket was cancelled
Errno::EINPROGRESS - a blocking socket is in progress or the service provider is still processing a callback function. Or a nonblocking connect call is in progress on the socket.
Errno::EALREADY - see Errno::EINVAL
Errno::EADDRNOTAVAIL - the remote address is not a valid address, such as ADDR_ANY TODO check ADDRANY TO INADDR_ANY
Errno::EAFNOSUPPORT - addresses in the specified family cannot be used with with this socket
Errno::ECONNREFUSED - the target sockaddr was not listening for connections refused the connection request
Errno::EFAULT - the socket’s internal address or address length parameter is too small or is not a valid part of the user space address
Errno::EINVAL - the socket is a listening socket
Errno::EISCONN - the socket is already connected
Errno::ENETUNREACH - the network cannot be reached from this host at this time
Errno::EHOSTUNREACH - no route to the network is present
Errno::ENOBUFS - no buffer space is available
Errno::ENOTSOCK - the socket argument does not refer to a socket
Errno::ETIMEDOUT - the attempt to connect timed out before a connection was made.
Errno::EWOULDBLOCK - the socket is marked as nonblocking and the connection cannot be completed immediately
Errno::EACCES - the attempt to connect the datagram socket to the broadcast address failed

See¶ ↑

connect manual pages on unix-based systems
connect function in Microsoft’s Winsock functions reference

static VALUE
sock_connect(VALUE sock, VALUE addr)
{
    VALUE rai;
    rb_io_t *fptr;
    int fd, n;

    SockAddrStringValueWithAddrinfo(addr, rai);
    addr = rb_str_new4(addr);
    GetOpenFile(sock, fptr);
    fd = fptr->fd;
    n = rsock_connect(fd, (struct sockaddr*)RSTRING_PTR(addr), RSTRING_SOCKLEN(addr), 0, NULL);
    if (n < 0) {
        rsock_sys_fail_raddrinfo_or_sockaddr("connect(2)", addr, rai);
    }

    return INT2FIX(n);
}

connect_nonblock(remote_sockaddr, [options]) → 0

Requests a connection to be made on the given remote_sockaddr after O_NONBLOCK is set for the underlying file descriptor. Returns 0 if successful, otherwise an exception is raised.

Parameter¶ ↑

# +remote_sockaddr+ - the +struct+ sockaddr contained in a string or Addrinfo object

Example:¶ ↑

# Pull down Google's web page
require 'socket'
include Socket::Constants
socket = Socket.new(AF_INET, SOCK_STREAM, 0)
sockaddr = Socket.sockaddr_in(80, 'www.google.com')
begin # emulate blocking connect
  socket.connect_nonblock(sockaddr)
rescue IO::WaitWritable
  IO.select(nil, [socket]) # wait 3-way handshake completion
  begin
    socket.connect_nonblock(sockaddr) # check connection failure
  rescue Errno::EISCONN
  end
end
socket.write("GET / HTTP/1.0\r\n\r\n")
results = socket.read

Refer to Socket#connect for the exceptions that may be thrown if the call to connect_nonblock fails.

Socket#connect_nonblock may raise any error corresponding to connect(2) failure, including Errno::EINPROGRESS.

If the exception is Errno::EINPROGRESS, it is extended by IO::WaitWritable. So IO::WaitWritable can be used to rescue the exceptions for retrying connect_nonblock.

By specifying a keyword argument exception to false, you can indicate that connect_nonblock should not raise an IO::WaitWritable exception, but return the symbol :wait_writable instead.

See¶ ↑

# Socket#connect

# File ext/socket/lib/socket.rb, line 1625
def connect_nonblock(addr, exception: true)
  __connect_nonblock(addr, exception)
end

ipv6only! ()

enable the socket option IPV6_V6ONLY if IPV6_V6ONLY is available.

# File ext/socket/lib/socket.rb, line 468
def ipv6only!
  if defined? Socket::IPV6_V6ONLY
    self.setsockopt(:IPV6, :V6ONLY, 1)
  end
end

listen( int ) → 0

Listens for connections, using the specified int as the backlog. A call to listen only applies if the socket is of type SOCK_STREAM or SOCK_SEQPACKET.

Parameter¶ ↑

backlog - the maximum length of the queue for pending connections.

Example 1¶ ↑

require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
socket.bind( sockaddr )
socket.listen( 5 )

Example 2 (listening on an arbitrary port, unix-based systems only):¶ ↑

require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
socket.listen( 1 )

Unix-based Exceptions¶ ↑

On unix based systems the above will work because a new sockaddr struct is created on the address ADDR_ANY, for an arbitrary port number as handed off by the kernel. It will not work on Windows, because Windows requires that the socket is bound by calling bind before it can listen.

If the backlog amount exceeds the implementation-dependent maximum queue length, the implementation’s maximum queue length will be used.

On unix-based based systems the following system exceptions may be raised if the call to listen fails:

Errno::EBADF - the socket argument is not a valid file descriptor
Errno::EDESTADDRREQ - the socket is not bound to a local address, and the protocol does not support listening on an unbound socket
Errno::EINVAL - the socket is already connected
Errno::ENOTSOCK - the socket argument does not refer to a socket
Errno::EOPNOTSUPP - the socket protocol does not support listen
Errno::EACCES - the calling process does not have appropriate privileges
Errno::EINVAL - the socket has been shut down
Errno::ENOBUFS - insufficient resources are available in the system to complete the call

Windows Exceptions¶ ↑

On Windows systems the following system exceptions may be raised if the call to listen fails:

Errno::ENETDOWN - the network is down
Errno::EADDRINUSE - the socket’s local address is already in use. This usually occurs during the execution of bind but could be delayed if the call to bind was to a partially wildcard address (involving ADDR_ANY) and if a specific address needs to be committed at the time of the call to listen
Errno::EINPROGRESS - a Windows Sockets 1.1 call is in progress or the service provider is still processing a callback function
Errno::EINVAL - the socket has not been bound with a call to bind.
Errno::EISCONN - the socket is already connected
Errno::EMFILE - no more socket descriptors are available
Errno::ENOBUFS - no buffer space is available
Errno::ENOTSOC - socket is not a socket
Errno::EOPNOTSUPP - the referenced socket is not a type that supports the listen method

See¶ ↑

listen manual pages on unix-based systems
listen function in Microsoft’s Winsock functions reference

VALUE
rsock_sock_listen(VALUE sock, VALUE log)
{
    rb_io_t *fptr;
    int backlog;

    backlog = NUM2INT(log);
    GetOpenFile(sock, fptr);
    if (listen(fptr->fd, backlog) < 0)
        rb_sys_fail("listen(2)");

    return INT2FIX(0);
}

recvfrom(maxlen) → [mesg, sender_addrinfo]

recvfrom(maxlen, flags) → [mesg, sender_addrinfo]

Receives up to maxlen bytes from socket. flags is zero or more of the MSG_ options. The first element of the results, mesg, is the data received. The second element, sender_addrinfo, contains protocol-specific address information of the sender.

Parameters¶ ↑

maxlen - the maximum number of bytes to receive from the socket
flags - zero or more of the MSG_ options

Example¶ ↑

# In one file, start this first
require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
socket.bind( sockaddr )
socket.listen( 5 )
client, client_addrinfo = socket.accept
data = client.recvfrom( 20 )[0].chomp
puts "I only received 20 bytes '#{data}'"
sleep 1
socket.close

# In another file, start this second
require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
socket.connect( sockaddr )
socket.puts "Watch this get cut short!"
socket.close

Unix-based Exceptions¶ ↑

On unix-based based systems the following system exceptions may be raised if the call to recvfrom fails:

Errno::EAGAIN - the socket file descriptor is marked as O_NONBLOCK and no data is waiting to be received; or MSG_OOB is set and no out-of-band data is available and either the socket file descriptor is marked as O_NONBLOCK or the socket does not support blocking to wait for out-of-band-data
Errno::EWOULDBLOCK - see Errno::EAGAIN
Errno::EBADF - the socket is not a valid file descriptor
Errno::ECONNRESET - a connection was forcibly closed by a peer
Errno::EFAULT - the socket’s internal buffer, address or address length cannot be accessed or written
Errno::EINTR - a signal interrupted recvfrom before any data was available
Errno::EINVAL - the MSG_OOB flag is set and no out-of-band data is available
Errno::EIO - an i/o error occurred while reading from or writing to the filesystem
Errno::ENOBUFS - insufficient resources were available in the system to perform the operation
Errno::ENOMEM - insufficient memory was available to fulfill the request
Errno::ENOSR - there were insufficient STREAMS resources available to complete the operation
Errno::ENOTCONN - a receive is attempted on a connection-mode socket that is not connected
Errno::ENOTSOCK - the socket does not refer to a socket
Errno::EOPNOTSUPP - the specified flags are not supported for this socket type
Errno::ETIMEDOUT - the connection timed out during connection establishment or due to a transmission timeout on an active connection

Windows Exceptions¶ ↑

On Windows systems the following system exceptions may be raised if the call to recvfrom fails:

Errno::ENETDOWN - the network is down
Errno::EFAULT - the internal buffer and from parameters on socket are not part of the user address space, or the internal fromlen parameter is too small to accommodate the peer address
Errno::EINTR - the (blocking) call was cancelled by an internal call to the WinSock function WSACancelBlockingCall
Errno::EINPROGRESS - a blocking Windows Sockets 1.1 call is in progress or the service provider is still processing a callback function
Errno::EINVAL - socket has not been bound with a call to bind, or an unknown flag was specified, or MSG_OOB was specified for a socket with SO_OOBINLINE enabled, or (for byte stream-style sockets only) the internal len parameter on socket was zero or negative
Errno::EISCONN - socket is already connected. The call to recvfrom is not permitted with a connected socket on a socket that is connection oriented or connectionless.
Errno::ENETRESET - the connection has been broken due to the keep-alive activity detecting a failure while the operation was in progress.
Errno::EOPNOTSUPP - MSG_OOB was specified, but socket is not stream-style such as type SOCK_STREAM. OOB data is not supported in the communication domain associated with socket, or socket is unidirectional and supports only send operations
Errno::ESHUTDOWN - socket has been shutdown. It is not possible to call recvfrom on a socket after shutdown has been invoked.
Errno::EWOULDBLOCK - socket is marked as nonblocking and a call to recvfrom would block.
Errno::EMSGSIZE - the message was too large to fit into the specified buffer and was truncated.
Errno::ETIMEDOUT - the connection has been dropped, because of a network failure or because the system on the other end went down without notice
Errno::ECONNRESET - the virtual circuit was reset by the remote side executing a hard or abortive close. The application should close the socket; it is no longer usable. On a UDP-datagram socket this error indicates a previous send operation resulted in an ICMP Port Unreachable message.

static VALUE
sock_recvfrom(int argc, VALUE *argv, VALUE sock)
{
    return rsock_s_recvfrom(sock, argc, argv, RECV_SOCKET);
}

recvfrom_nonblock(maxlen[, flags[, outbuf[, opts]]]) → [mesg, sender_addrinfo]

Receives up to maxlen bytes from socket using recvfrom(2) after O_NONBLOCK is set for the underlying file descriptor. flags is zero or more of the MSG_ options. The first element of the results, mesg, is the data received. The second element, sender_addrinfo, contains protocol-specific address information of the sender.

When recvfrom(2) returns 0, Socket#recv_nonblock returns nil. In most cases it means the connection was closed, but for UDP connections it may mean an empty packet was received, as the underlying API makes it impossible to distinguish these two cases.

Parameters¶ ↑

maxlen - the maximum number of bytes to receive from the socket
flags - zero or more of the MSG_ options
outbuf - destination String buffer
opts - keyword hash, supporting ‘exception: false`

Example¶ ↑

# In one file, start this first
require 'socket'
include Socket::Constants
socket = Socket.new(AF_INET, SOCK_STREAM, 0)
sockaddr = Socket.sockaddr_in(2200, 'localhost')
socket.bind(sockaddr)
socket.listen(5)
client, client_addrinfo = socket.accept
begin # emulate blocking recvfrom
  pair = client.recvfrom_nonblock(20)
rescue IO::WaitReadable
  IO.select([client])
  retry
end
data = pair[0].chomp
puts "I only received 20 bytes '#{data}'"
sleep 1
socket.close

# In another file, start this second
require 'socket'
include Socket::Constants
socket = Socket.new(AF_INET, SOCK_STREAM, 0)
sockaddr = Socket.sockaddr_in(2200, 'localhost')
socket.connect(sockaddr)
socket.puts "Watch this get cut short!"
socket.close

Refer to Socket#recvfrom for the exceptions that may be thrown if the call to recvfrom_nonblock fails.

Socket#recvfrom_nonblock may raise any error corresponding to recvfrom(2) failure, including Errno::EWOULDBLOCK.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by IO::WaitReadable. So IO::WaitReadable can be used to rescue the exceptions for retrying recvfrom_nonblock.

By specifying a keyword argument exception to false, you can indicate that recvfrom_nonblock should not raise an IO::WaitReadable exception, but return the symbol :wait_readable instead.

See¶ ↑

Socket#recvfrom

# File ext/socket/lib/socket.rb, line 541
def recvfrom_nonblock(len, flag = 0, str = nil, exception: true)
  __recvfrom_nonblock(len, flag, str, exception)
end

sysaccept → [client_socket_fd, client_addrinfo]

Accepts an incoming connection returning an array containing the (integer) file descriptor for the incoming connection, client_socket_fd, and an Addrinfo, client_addrinfo.

Example¶ ↑

# In one script, start this first
require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
socket.bind( sockaddr )
socket.listen( 5 )
client_fd, client_addrinfo = socket.sysaccept
client_socket = Socket.for_fd( client_fd )
puts "The client said, '#{client_socket.readline.chomp}'"
client_socket.puts "Hello from script one!"
socket.close

# In another script, start this second
require 'socket'
include Socket::Constants
socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
socket.connect( sockaddr )
socket.puts "Hello from script 2."
puts "The server said, '#{socket.readline.chomp}'"
socket.close

Refer to Socket#accept for the exceptions that may be thrown if the call to sysaccept fails.

See¶ ↑

Socket#accept

static VALUE
sock_sysaccept(VALUE server)
{
    union_sockaddr buffer;
    socklen_t length = (socklen_t)sizeof(buffer);

    VALUE peer = rsock_s_accept(0, server, &buffer.addr, &length);

    return rb_assoc_new(peer, rsock_io_socket_addrinfo(peer, &buffer.addr, length));
}

class Socket

What’s a socket?¶ ↑

Quick start¶ ↑

Exception Handling¶ ↑

Convenience methods¶ ↑

Documentation by¶ ↑

Example¶ ↑

See¶ ↑

Parameter¶ ↑

Example¶ ↑

Unix-based Exceptions¶ ↑

Windows Exceptions¶ ↑

See¶ ↑

Parameter¶ ↑

Example:¶ ↑

Unix-based Exceptions¶ ↑

Windows Exceptions¶ ↑

See¶ ↑

Parameter¶ ↑

Example:¶ ↑

See¶ ↑

Parameter¶ ↑

Example 1¶ ↑

Example 2 (listening on an arbitrary port, unix-based systems only):¶ ↑

Unix-based Exceptions¶ ↑

Windows Exceptions¶ ↑

See¶ ↑

Parameters¶ ↑

Example¶ ↑

Unix-based Exceptions¶ ↑

Windows Exceptions¶ ↑

Parameters¶ ↑

Example¶ ↑

See¶ ↑

Example¶ ↑

See¶ ↑

`Exception` Handling¶ ↑