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:

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:

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 ↑

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