Socket Programming in Ruby

Published in

Code Like A Girl

3 min readSep 19, 2017

Sockets are the endpoints of the communication channel, both clients and servers have to use sockets to communicate.
Once a connection is established you can put data into your socket and it will make its way to the other end, where the receiver will read from the socket to process incoming packets.

Using Sockets in Ruby
TCP Server
We need to tell the socket to bind to an interface, then listen on it, and finally to accept incoming connections.

require 'socket'

puts "Starting the Server..................."
server = TCPServer.open(3000) # Server would listen on port 3000
loop{                         # Servers run forever
   client_connection = server.accept # Establish client connect connection
   client_connection.puts(Time.now) # Send the time to the client
   client_connection.puts("Closing the connection with #{client_connection}")
   client_connection.close      # Disconnect from the client
}

TCP Client

require 'socket'

socket = TCPSocket.open("localhost", 3000)

puts "Starting the Client..................."
while message = socket.gets             # Read lines from the socket
   puts message.chomp
end

puts "Closing the Client..................."
socket.close                    # Close the socket

Accepting Multiple Clients

Let’s modify our server in order to handle multiple client request.

require 'socket'

puts "Starting the Server..................."
server = TCPServer.open(3000) # Server would listen on port 3000
loop{                         # Servers run forever
   client_connection = server.accept # Establish client connect connection
   Thread.start(client_connection) do |connection|
      connection.puts(Time.now) # Send the time to the client
      connection.puts("Closing the connection with #{client_connection}")
      connection.close      # Disconnect from the client
   end
}

Let’s build a small application to establish end-to-end communication:

Server

require 'socket'

class Server
   def initialize(socket_address, socket_port)
      @server_socket = TCPServer.open(socket_port, socket_address)

      @connections_details = Hash.new
      @connected_clients = Hash.new

      @connections_details[:server] = @server_socket
      @connections_details[:clients] = @connected_clients

      puts 'Started server.........'
      run

   end

   def run
      loop{
         client_connection = @server_socket.accept
         Thread.start(client_connection) do |conn| # open thread for each accepted connection
            conn_name = conn.gets.chomp.to_sym
            if(@connections_details[:clients][conn_name] != nil) # avoid connection if user exits
               conn.puts "This username already exist"
               conn.puts "quit"
               conn.kill self
            end

            puts "Connection established #{conn_name} => #{conn}"
            @connections_details[:clients][conn_name] = conn
            conn.puts "Connection established successfully #{conn_name} => #{conn}, you may continue with chatting....."

            establish_chatting(conn_name, conn) # allow chatting
         end
      }.join
   end

   def establish_chatting(username, connection)
      loop do
         message = connection.gets.chomp
         puts @connections_details[:clients]
         (@connections_details[:clients]).keys.each do |client|
            @connections_details[:clients][client].puts "#{username} : #{message}"
         end
      end
   end
end


Server.new( 8080, "localhost" )

Client side

require 'socket'

class Client
   def initialize(socket)
      @socket = socket
      @request_object = send_request
      @response_object = listen_response

      @request_object.join # will send the request to server
      @response_object.join # will receive response from server
   end

   def send_request
      puts "Please enter your username to establish a connection..."
      begin
         Thread.new do
            loop do
               message = $stdin.gets.chomp
               @socket.puts message
            end
         end
      rescue IOError => e
         puts e.message
         # e.backtrace
         @socket.close
      end

   end

   def listen_response
      begin
         Thread.new do
            loop do
               response = @socket.gets.chomp
               puts "#{response}"
               if response.eql?'quit'
                  @socket.close
               end
            end
         end
      rescue IOError => e
         puts e.message
         # e.backtrace
         @socket.close
      end
   end
end



socket = TCPSocket.open( "localhost", 8080 )
Client.new( socket )