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Class: Socket

Relationships & Source Files
Namespace Children
Modules:
Classes:
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
Instance Chain:
Inherits: BasicSocket
Defined in: ext/socket/socket.c,
ext/socket/constdefs.c,
ext/socket/ifaddr.c,
ext/socket/lib/socket.rb

Overview

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 Constants are also defined under Socket. For example, AF_INET is usable as well as Constants::AF_INET. See 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:

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

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:

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 .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.

Constant Summary

Class Attribute Summary

::BasicSocket - Inherited

.do_not_reverse_lookup

Gets the global do_not_reverse_lookup flag.

.do_not_reverse_lookup=

Sets the global do_not_reverse_lookup flag.

Class Method Summary

::BasicSocket - Inherited

.for_fd

Returns a socket object which contains the file descriptor, fd.

Instance Attribute Summary

::BasicSocket - Inherited

#do_not_reverse_lookup

Gets the do_not_reverse_lookup flag of basicsocket.

#do_not_reverse_lookup=

Sets the do_not_reverse_lookup flag of basicsocket.

Instance Method Summary

::BasicSocket - Inherited

#close_read

Disallows further read using shutdown system call.

#close_write

Disallows further write using shutdown system call.

#connect_address

Returns an address of the socket suitable for connect in the local machine.

#getpeereid

Returns the user and group on the peer of the UNIX socket.

#getpeername

Returns the remote address of the socket as a sockaddr string.

#getsockname

Returns the local address of the socket as a sockaddr string.

#getsockopt

Gets a socket option.

#local_address

Returns an ::Addrinfo object for local address obtained by getsockname.

#recv

Receives a message.

#recv_nonblock

Receives up to maxlen bytes from socket using recvfrom(2) after O_NONBLOCK is set for the underlying file descriptor.

#recvmsg

recvmsg receives a message using recvmsg(2) system call in blocking manner.

#recvmsg_nonblock

recvmsg receives a message using recvmsg(2) system call in non-blocking manner.

#remote_address

Returns an ::Addrinfo object for remote address obtained by getpeername.

#send

send mesg via basicsocket.

#sendmsg

sendmsg sends a message using sendmsg(2) system call in blocking manner.

#sendmsg_nonblock

sendmsg_nonblock sends a message using sendmsg(2) system call in non-blocking manner.

#setsockopt

Sets a socket option.

#shutdown

Calls shutdown(2) system call.

Constructor Details

.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

Class Method Details

.accept_loop(*sockets)

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.

[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 496

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|
      begin
        sock, addr = r.accept_nonblock
      rescue IO::WaitReadable
        next
      end
      yield sock, addr
    }
  }
end

.getaddrinfo(nodename, servname[, family[, socktype[, protocol[, flags[, reverse_lookup]]]]]) ⇒ Array

Obtains address information for nodename:servname.

family should be an address family 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 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.

.gethostbyaddr(address_string [, address_family]) ⇒ hostent

Obtains the host information for address.

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

.gethostbyname(hostname) ⇒ Array, ...

Obtains the host information for hostname.

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

.gethostnamehostname

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.

.getifaddrsArray, ...

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)>]

.getnameinfo(sockaddr [, flags]) ⇒ Array, 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.

.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

.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"

.ip_address_listArray

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>,
     #...]

.sockaddr_in(port, host) ⇒ sockaddr .pack_sockaddr_in(port, host) ⇒ sockaddr

Alias for .sockaddr_in.

.sockaddr_un(path) ⇒ sockaddr .pack_sockaddr_un(path) ⇒ sockaddr

Alias for .sockaddr_un.

.pair(domain, type, protocol) ⇒ Socket .socketpair(domain, type, protocol) ⇒ Socket
Also known as: .socketpair

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"

.sockaddr_in(port, host) ⇒ sockaddr .pack_sockaddr_in(port, host) ⇒ sockaddr
Also known as: .pack_sockaddr_in

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"

.sockaddr_un(path) ⇒ sockaddr .pack_sockaddr_un(path) ⇒ sockaddr
Also known as: .pack_sockaddr_un

Packs path as an AF_UNIX sockaddr string.

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

.pair(domain, type, protocol) ⇒ Socket .socketpair(domain, type, protocol) ⇒ Socket

Alias for .pair.

.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:

: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
}

Raises:

  • (ArgumentError)
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 314

def self.tcp(host, port, *rest) # :yield: socket
  opts = Hash === rest.last ? rest.pop : {}
  raise ArgumentError, "wrong number of arguments (#{rest.length} for 2)" if 2 < rest.length
  local_host, local_port = rest
  last_error = nil
  ret = nil

  connect_timeout = opts[:connect_timeout]

  local_addr_list = nil
  if local_host != nil || local_port != nil
    local_addr_list = Addrinfo.getaddrinfo(local_host, local_port, nil, :STREAM, nil)
  end

  Addrinfo.foreach(host, port, nil, :STREAM) {|ai|
    if local_addr_list
      local_addr = local_addr_list.find {|local_ai| local_ai.afamily == ai.afamily }
      next if !local_addr
    else
      local_addr = nil
    end
    begin
      sock = local_addr ?
        ai.connect_from(local_addr, :timeout => connect_timeout) :
        ai.connect(:timeout => connect_timeout)
    rescue SystemCallError
      last_error = $!
      next
    end
    ret = sock
    break
  }
  if !ret
    if last_error
      raise last_error
    else
      raise SocketError, "no appropriate local address"
    end
  end
  if block_given?
    begin
      yield ret
    ensure
      ret.close if !ret.closed?
    end
  else
    ret
  end
end

.tcp_server_loop(host = nil, port, &b)

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
  }
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 555

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)

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>]
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 452

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 {|s| s.close }
      raise
    end
  end
  if block_given?
    begin
      yield sockets
    ensure
      sockets.each {|s| s.close if !s.closed? }
    end
  else
    sockets
  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
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 727

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 .udp_server_sockets is appropriate for the argument.

It calls the block for each message received.

[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 700

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.

.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| ... }
  }
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 670

def self.udp_server_recv(sockets)
  sockets.each {|r|
    begin
      msg, sender_addrinfo, _, *controls = r.recvmsg_nonblock
    rescue IO::WaitReadable
      next
    end
    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
  }
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 583

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 if !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 if !a.ipv6?
        ip_list << Addrinfo.new(a.to_sockaddr, :INET6, :DGRAM, 0);
      }
    else
      ip_list << ai
    end
  }

  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 {|s| s.close if !s.closed? } if sockets
    end
  else
    sockets
  end
end

.unix(path)

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
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 777

def self.unix(path) # :yield: socket
  addr = Addrinfo.unix(path)
  sock = addr.connect
  if block_given?
    begin
      yield sock
    ensure
      sock.close if !sock.closed?
    end
  else
    sock
  end
end

.unix_server_loop(path, &b)

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
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 864

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)

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>
}
[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 807

def self.unix_server_socket(path)
  if !unix_socket_abstract_name?(path)
    begin
      st = File.lstat(path)
    rescue Errno::ENOENT
    end
    if st && st.socket? && st.owned?
      File.unlink path
    end
  end
  s = Addrinfo.unix(path).listen
  if block_given?
    begin
      yield s
    ensure
      s.close if !s.closed?
      if !unix_socket_abstract_name?(path)
        File.unlink path
      end
    end
  else
    s
  end
end

.unix_socket_abstract_name?(path) ⇒ Boolean (private)

[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 835

def unix_socket_abstract_name?(path)
  /linux/ =~ RUBY_PLATFORM && /\A(\0|\z)/ =~ path
end

.unpack_sockaddr_in(sockaddr) ⇒ Array, 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"]

.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"

Instance Method Details

#acceptSocket, 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>]

#accept_nonblockSocket, 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 #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::AGAIN, 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.

See

#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 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

#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 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

#connect_nonblock(remote_sockaddr) ⇒ 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 #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.

See

#ipv6only!

enable the socket option IPV6_V6ONLY if IPV6_V6ONLY is available.

[ GitHub ]

  
# File 'ext/socket/lib/socket.rb', line 282

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

#recvfrom(maxlen) ⇒ Array, sender_addrinfo #recvfrom(maxlen, flags) ⇒ Array, 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.

#recvfrom_nonblock(maxlen) ⇒ Array, sender_addrinfo #recvfrom_nonblock(maxlen, flags) ⇒ Array, 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, recvfrom_nonblock returns an empty string as data. The meaning depends on the socket: EOF on TCP, empty packet on UDP, etc.

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

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

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

See

#sysacceptSocket, 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 #accept for the exceptions that may be thrown if the call to sysaccept fails.

See