Various implementations of echo server.

echo_server.php

<?php
$server = socket_create_listen(12345);
echo "Listening..." . PHP_EOL;
while (true) {
    $client        = socket_accept($server);
    $receivedInput = chop(socket_read($client, 1024));
    echo "Received Input: " . $receivedInput . PHP_EOL;
    if (strlen($receivedInput) === 0) {
        break;
    }
    socket_write($client, $receivedInput . PHP_EOL);
    socket_close($client);
}
socket_close($server);
echo "Good bye." . PHP_EOL;

echo_server.pl

use strict;
use warnings;
use Socket;

socket(SERVER, PF_INET, SOCK_STREAM, 0);
setsockopt(SERVER, SOL_SOCKET, SO_REUSEADDR, 1);
bind(SERVER, pack_sockaddr_in(12345, INADDR_ANY));
listen(SERVER, SOMAXCONN);
print "Listening...$/";
while (1) {
  my $client = accept(CLIENT, SERVER);
  my ($client_port, $client_iaddr) = unpack_sockaddr_in($client);
  my ($client_ip) = inet_ntoa($client_iaddr);
  my $received_input = <CLIENT>;
  $received_input =~ s/(\r\n|\r|\n)$//g;
  print "Received Input: $received_input$/";
  last if ($received_input eq '');
  print CLIENT $received_input . $/;
  close(CLIENT);
}
close(SERVER);
print "Good bye.$/";

echo_server.py

import socket

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server.bind(('', 12345))
server.listen(5)
print "Listening..."
while 1:
  client, addr = server.accept()
  received_input = client.recv(1024).rstrip()
  print received_input
  if received_input == '':
    break
  client.send(received_input + "\n")
  client.close()
print "Good bye."

echo_server.rb

require 'socket'

TCPServer.open(12345) do |server|
  puts "Listening..."
  loop do
    client         = server.accept
    received_input = client.gets.chomp
    puts "Received Input: " + received_input
    break if received_input.size == 0
    client.puts received_input
    client.close
  end
end
puts "Good bye."