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 bidirectionnal 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:


The family of protocols: Socket::PF_INET, Socket::PF_INET6, Socket::PF_UNIX, etc.


The type of communications between the two endpoints, typically Socket::SOCK_STREAM or Socket::SOCK_DGRAM.


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


The identifier of a network interface:

* a string (hostname, IPv4 or IPv6 adress or <tt><broadcast></tt>
  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

Some classes such as TCPSocket, UDPSocket or UNIXSocket ease use of sockets of these types compared to C programming.

# Creating a TCP socket in a C-like manner
s = Socket.new Socket::INET, Socket::SOCK_STREAM
s.connect Socket.pack_sockaddr_in(80, 'example.com')

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

A simple server would look like:

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}"

A simple client may look like:

require 'socket'

s = TCPSocket.new 'localhost', 2000

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

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 particular exception is needed please refer to the Unix manual pages or the Windows WinSock reference.

Convenient methods

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


AF_INET6 = Object.new


Show files where this class is defined (3 files)
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