Class: Socket

Obtains address information for nodename:servname.

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 same as numeric address.
nil:              obey to the current do_not_reverse_lookup flag.

If Addrinfo object is preferred, use Addrinfo.getaddrinfo.

Obtains the host information for address.

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

Obtains the host information for hostname.

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

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 .ip_address_list.

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)>]

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.

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

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"

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>,
     #...]

Alias for .sockaddr_in.

Alias for .sockaddr_un.

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"

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"

Packs path as an AF_UNIX sockaddr string.

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

Alias for .pair.

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:

:connect_timeout

specify the timeout in seconds.

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
}

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. 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
  }
}

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>]
}

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
}

Run UDP/IP server loop on the given sockets.

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

It calls the block for each message received.

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.

.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| ... }
  }
}

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
  }
}

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
}

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
}

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>
}

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"]

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"

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

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

• #accept

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 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

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 time 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 time 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

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

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