$host = "127.0.0.1";
$port = 25003;
// don't timeout!
set_time_limit(0);
// create socket
$socket = socket_create(AF_INET, SOCK_STREAM, 0) or die("Could not create socketn");
// bind socket to port
$result = socket_bind($socket, $host, $port) or die("Could not bind to socketn");
// start listening for connections
$result = socket_listen($socket, 3) or die("Could not set up socket listenern");

// accept incoming connections
// spawn another socket to handle communication
$spawn = socket_accept($socket) or die("Could not accept incoming connectionn");
// read client input
$input = socket_read($spawn, 1024) or die("Could not read inputn");
// clean up input string
$input = trim($input);
echo "Client Message : ".$input;
// reverse client input and send back
$output = strrev($input) . "n";
socket_write($spawn, $output, strlen ($output)) or die("Could not write outputn");
// close sockets
socket_close($spawn);
socket_close($socket);

$ php -q test.php &
[1] 2855

# Now we try again a SECOND copy...
$ php -q test.php

PHP Warning:  socket_bind(): unable to bind address [98]: Address already in use in test.php on line 9
Could not bind to socket

$ telnet 127.0.0.1 25003
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
HELLO WORLD.
Client Message : HELLO WORLD..DLROW OLLEH
Connection closed by foreign host.