Ruby Simple TCP Echo Servers

01_sequential.rb

#!/usr/bin/env ruby
require './common.rb'
require 'socket'

def main
  server = server_socket('0.0.0.0', 1024)
  loop do
    handle_client(*server.accept)
  end

  0 # Return code
end

exit main || 0 if __FILE__ == $PROGRAM_NAME

02_forking.rb

#!/usr/bin/env ruby
require './common.rb'
require 'socket'

def main
  server = server_socket('0.0.0.0', 1024)
  loop do
    # TODO: Clean up terminated child processes
    client, addrinfo = server.accept
    if fork
      client.close  # Clean up on server
    else
      server.close  # Clean up on client
      handle_client(client, addrinfo)
      break
    end
  end

  0 # Return code
end

exit main || 0 if __FILE__ == $PROGRAM_NAME

03_process_pool.rb

#!/usr/bin/env ruby
require './common.rb'
require 'socket'

def clean_up_children
  loop do
    Process.wait # Gather processes as they exit
  end
rescue Interrupt
  Process.kill('HUP', 0) # Kill all children when main process is terminated
rescue SystemCallError
  puts 'All children have exited. Goodbye!'
end

def main
  server = server_socket('0.0.0.0', 1024)

  4.times do # Adjust this number for the pool size
    next unless fork.nil? # Parent only calls fork
    loop do # Child does this work
      handle_client(*server.accept)
    end
    return 0
  end

  clean_up_children
  0 # Return code
end

exit main || 0 if __FILE__ == $PROGRAM_NAME

common.rb

def handle_client(client, addrinfo)
  send(client, "   Connected: #{addrinfo.inspect}\n")

  begin
    process_requests(client)
    puts "Disconnected: #{addrinfo.inspect}\n"
  rescue Errno::ECONNRESET, Errno::EPIPE
    puts "       Reset: #{addrinfo.inspect}\n"
  end

  client.close
end

def process_requests(socket)
  data = socket.recv(1024)
  while data != ''
    send(socket, data)
    data = socket.recv(1024)
  end
end

def send(socket, message)
  print message
  socket.write(message)
end

def server_socket(addr, port)
  socket = Socket.new(:INET, :SOCK_STREAM)
  socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_REUSEADDR, true)
  socket.bind(Addrinfo.tcp(addr, port))
  socket.listen(1)
  puts 'Waiting for connections...'
  socket
end