IPv6 protocol family

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:

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 adress 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

::tcp, IO.open

TCP server socket

::tcp_server_loop, IO.open

UNIX client socket

::unix, IO.open

UNIX server socket

::unix_server_loop, IO.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.