PHP time server (example PHP server implementation). Run the server from command line, specifying port parameter and connect to it from outside (could be any platform that is able to open a socket or just a telnet connection: `telnet localhost <port>`). The server writes back current time in RFC 2822 and immediately closes the connection.

time-server.php

#!/usr/bin/php -q
<?php

set_time_limit(0);
ob_implicit_flush();

if ($argc != 2)
    die("Simple Time Server (C) 2013 Tomasz Ducin\n" .
        "Invalid parameters passed\n" .
        "Run:\n\t./time-server.php <port>\n" .
        "Example:\n\t./time-server.php 12345\n");

$address = 'localhost';
$port = $argv[1];

if (($sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) === false)
    die(socket_strerror(socket_last_error()) . "\n");

if (socket_bind($sock, $address, $port) === false)
    die(socket_strerror(socket_last_error($sock)) . "\n");

if (socket_listen($sock, 5) === false)
    die(socket_strerror(socket_last_error($sock)) . "\n");

socket_set_nonblock($sock);

$remote_host = $remote_port = $msgsock = null;

declare(ticks = 1);

function sig_handler($signo)
{
    switch ($signo) {
        case SIGTERM:
        case SIGINT:
            // do your persistence here
            global $sock;
            socket_shutdown($sock);
            socket_close($sock);
            echo "Terminating...\n";
            exit;
    }
}

pcntl_signal(SIGTERM, "sig_handler");
pcntl_signal(SIGINT, "sig_handler");

echo "Starting server\n";

while (1) {
    do {
        $msgsock = @socket_accept($sock);
        usleep(100000);
    } while ($msgsock === false);

    socket_getpeername($msgsock, $remote_host, $remote_port);
    echo "Connection made from {$remote_host}:{$remote_port}\n";

    $msg = date('r', time()) . "\n";
    socket_write($msgsock, $msg, strlen($msg));
    socket_close($msgsock);
};

socket_close($sock);