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====== Multi-Client_TCP_Server_Example ======

<source lang="php"><?php
 
/*****************************************************************************
 * PHP Multi-Client TCP Socket Example                                       *
 *****************************************************************************
 * Will listen on a given socket for TCP connections, echoing whatever data  *
 *  is sent to that socket.                                                  *
 *                                                                           *
 * Original script by KnoB in a comment in the PHP documentation:            *
 *  http://www.php.net/manual/en/ref.sockets.php#43155                       *
 *                                                                           *
 * Heavily modified and commented by Andrew Gillard                          *
 *****************************************************************************/
 
<nowiki>//</nowiki>What address are we listening on? This will have to be the same as in
<nowiki>//</nowiki> the client. You probably just want '127.0.0.1' for both.
$address = '127.0.0.1';
 
<nowiki>//</nowiki>What port to use? Again, the client will need to know this, too
$port = 10000;
 
?><!DOCTYPE html PUBLIC "-<nowiki>//</nowiki>W3C<nowiki>//</nowiki>DTD XHTML 1.0 Strict<nowiki>//</nowiki>EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
	<title>PHP Multi-Client Server Example</title>
	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
	<style type="text/css">
	div.error {
		padding: 0px 10px 5px 10px;
		background-color: #f88;
		border: 1px solid #f00;
	}
	div.error span {
		font-family: monospace;
	}
	</style>
</head>
<body>
 
<?php
 
<nowiki>//</nowiki>Disable PHP's script execution time limit
set_time_limit(0);
 
<nowiki>//</nowiki>Ensure that every time we call "echo", the data is sent to the browser
<nowiki>//</nowiki> IMMEDIATELY, rather than when PHP feels like it
ob_implicit_flush();
 
<nowiki>//</nowiki>Normally when the user clicks the "Stop" button in their browser, the
<nowiki>//</nowiki> script is terminated. This line stops that happening, so that we can
<nowiki>//</nowiki> detect the Stop button ourselves and properly close our sockets (to
<nowiki>//</nowiki> prevent the listening socket remaining open and stealing the port)
ignore_user_abort(true);
 
<nowiki>//</nowiki>Define a function that we can call when any of our socket function calls
<nowiki>//</nowiki> fail. This allows us to consolidate our error message XHTML and avoid
<nowiki>//</nowiki> code repetition. If $die is set to true, the script will terminate
function socketError($errorFunction, $die=false) {
	$errMsg = socket_strerror(socket_last_error());
 	
 	<nowiki>//</nowiki>This odd construct (known as a heredoc) just echos all of the text
 	<nowiki>//</nowiki> between "<<<EOHTML" and "EOHTML;". It's just a neater and easier to read
 	<nowiki>//</nowiki> format than using standard quoted strings. If you want to use one
 	<nowiki>//</nowiki> yourself, bear in mind that the structure is VERY strict: the opening
 	<nowiki>//</nowiki> line must be just "<<<" followed by the ending identifier, and the last
 	<nowiki>//</nowiki> line must contain NOTHING except the identifier ("EOHTML" in this case).
 	<nowiki>//</nowiki> The semi-colon after the closing identifier is optional, but it is
 	<nowiki>//</nowiki> important to realise that there cannot even be whitespace (tabs or
 	<nowiki>//</nowiki> spaces) before the EOHTML; at the end!!
	echo <<<EOHTML
<div class="error">
<h1>$errorFunction() failed!</h1>
<p>
	<strong>Error Message:</strong>
	<span>$errMsg</span>
</p>
<p>Note that if you have recently pressed your browser's Stop or
 Refresh/Reload button on this server script, you may have to wait a few
 seconds for the old server to release its listening port. As such, wait
 and try again in a few seconds.
</p>
</div>
EOHTML;
 
	if ($die) {
		<nowiki>//</nowiki>Close the BODY and HTML tags as well as terminating script 
		<nowiki>//</nowiki>execution because the die() call prevents us ever getting to the last
		<nowiki>//</nowiki> lines of this script
		die('</body></html>');
	}
}
 
<nowiki>//</nowiki>Attempt to create our socket. The "@" hides PHP's standard error reporting,
<nowiki>//</nowiki> so that we can output our own error message if it fails
if (!($server = @socket_create(AF_INET, SOCK_STREAM, SOL_TCP))) {
	socketError('socket_create', true);
}
 
<nowiki>//</nowiki>Set the "Reuse Address" socket option to enabled
socket_set_option($server, SOL_SOCKET, SO_REUSEADDR, 1);
 
<nowiki>//</nowiki>Attempt to bind our socket to the address and port that we're listening on.
<nowiki>//</nowiki> Again, we suppress PHP's error reporting in favour of our own
if (!@socket_bind($server, $address, $port)) {
	socketError('socket_bind', true);
}
 
<nowiki>//</nowiki>Start listening on the address and port that we bound our socket to above,
<nowiki>//</nowiki> using our own error reporting code as before
if (!@socket_listen($server)) {
	socketError('socket_listen', true);
}
 
<nowiki>//</nowiki>Create an array to store our sockets in. We use this so that we can
<nowiki>//</nowiki> determine which socket has new incoming data with the "socket_select()"
<nowiki>//</nowiki> function, and to properly close each socket when the script finishes
$allSockets = array($server);
 
<nowiki>//</nowiki>Start looping indefinitely. On each iteration we will make sure the browser's
<nowiki>//</nowiki> "Stop" button hasn't been pressed and, if not, see if we have any incoming
<nowiki>//</nowiki> client connection requests or any incoming data on existing clients
while (true) {
	<nowiki>//</nowiki>We have to echo something to the browser or PHP won't know if the Stop
	<nowiki>//</nowiki> button has been pressed
    echo ' ';
    if (connection_aborted()) {
    	<nowiki>//</nowiki>The Stop button has been pressed, so close all our sockets and exit
    	foreach ($allSockets as $socket) {
    		socket_close($socket);
		}
 
		<nowiki>//</nowiki>Now break out of this while() loop!
		break;
	}
 
	<nowiki>//</nowiki>socket_select() is slightly strange. You have to make a copy of the array
	<nowiki>//</nowiki> of sockets you pass to it, because it changes that array when it returns
	<nowiki>//</nowiki> and the resulting array will only contain sockets with waiting data on
	<nowiki>//</nowiki> them. $write and $except are set to NULL because we aren't interested in
	<nowiki>//</nowiki> them. The last parameter indicates that socket_select will return after
	<nowiki>//</nowiki> that many seconds if no data is receiveed in that time; this prevents the
	<nowiki>//</nowiki> script hanging forever at this point (remember, we might want to accept a
	<nowiki>//</nowiki> new connection or even exit entirely) and also pauses the script briefly
	<nowiki>//</nowiki> to prevent this tight while() loop using a lot of processor time
	$changedSockets = $allSockets;
	socket_select($changedSockets, $write = NULL, $except = NULL, 5);
 
	<nowiki>//</nowiki>Now we loop over each of the sockets that socket_select() says have new
	<nowiki>//</nowiki> data on them
	foreach($changedSockets as $socket) {
	    if ($socket == $server) {
	    	<nowiki>//</nowiki>socket_select() will include our server socket in the
	    	<nowiki>//</nowiki> $changedSockets array if there is an incoming connection attempt
	    	<nowiki>//</nowiki> on it. This will only accept one incoming connection per while()
	    	<nowiki>//</nowiki> loop iteration, but that shouldn't be a problem given the
	    	<nowiki>//</nowiki> frequency that we're iterating
	        if (!($client = @socket_accept($server))) {
	        	<nowiki>//</nowiki>socket_accept() failed for some reason (again, we hid PHP's
	        	<nowiki>//</nowiki> standard error message), so let's say what happened...
	        	socketError('socket_accept', false);
	        } else {
	        	<nowiki>//</nowiki>We've accepted the incoming connection, so add the new client
	        	<nowiki>//</nowiki> socket to our array of sockets
	        	$allSockets[[]] = $client;
	        }
	    } else {
			<nowiki>//</nowiki>Attempt to read data from this socket
	        $data = socket_read($socket, 2048);
	        if ($data === false || $data === //) {
            	<nowiki>//</nowiki>socket_read() returned FALSE, meaning that the client has
            	<nowiki>//</nowiki> closed the connection. Therefore we need to remove this
            	<nowiki>//</nowiki> socket from our client sockets array and close the socket
            	<nowiki>//</nowiki>A potential bug in PHP means that socket_read() will return
            	<nowiki>//</nowiki> an empty string instead of FALSE when the connection has
            	<nowiki>//</nowiki> been closed, contrary to what the documentation states. As
            	<nowiki>//</nowiki> such, we look for FALSE or an empty string (an empty string
            	<nowiki>//</nowiki> for the current, buggy, behaviour, and FALSE in case it ends
            	<nowiki>//</nowiki> up getting fixed at some point)
	            unset($allSockets[[array_search($socket,|$allSockets)]]);
	            socket_close($socket);
	        } else {
            	<nowiki>//</nowiki>We got useful data from socket_read(), so let's echo it.
            	<nowiki>//</nowiki> "$socket" will be output as "Resource id #n", where n is
            	<nowiki>//</nowiki> the internal ID of the socket, e.g. "Resource id #3"
            	<nowiki>//</nowiki>Note also that $data can be an empty string, so we check
            	<nowiki>//</nowiki> for that in our "elseif ($data)" line
				echo "\r\n<p><strong>&middot;</strong> $socket wrote: $data</p>";
	        }
	    }
	}
}
 
<nowiki>//</nowiki>Once we get here, the sockets have been closed, so just echo our XHTML footer
 
?>
 
</body>
</html></source>
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