FUNCTION blog about AS3, PHP 'n tech

Creating a PHP socket server

Socket server’s are great things for creating multiuse applications. Sockets are the most basic and thus efficient and quickest way for web applications Java, Flash, PHP, etc. to exchange data with eachother. With this you can create online multiplayer games, chat applications, mail and web servers, etc. Basically the only thing holding you back is your imagination. Most web dev’s however, don’t know how to create or use one. Well I found a way of creating a socket server with PHP. There’s not a lot of info about this on the web, but it is contrary to what many think a legal, possible and quite reliable use of PHP. It is actually even covered on the Zend Developer Zone. The code below is mainly based on that tutorial, but this one actually works in PHP5 and has been debugged a little further.

You will need three things for doing this tutorial;

• a PHP server enviroment at hand, because you will need to use your command line interface (don’t get affraid now, it’s easier than making web-apps)
• a way of creating PHP scripts; notepad, dreamweaver, etc.
• (if you want your socket server to run online) a free internet connected socket, which can pass through router, firewall, and is not beeing used by any other programs.

This is the debugged code, explanation is mainly in the comments and below;

<?php
// PHP SOCKET SERVER
error_reporting(E_ERROR);
// Configuration variables
$host = "127.0.0.1";
$port = 4041;
$max = 20;
$client = array();

// No timeouts, flush content immediatly
set_time_limit(0);
ob_implicit_flush();

// Server functions
function rLog($msg){
             $msg = "[".date('Y-m-d H:i:s')."] ".$msg;
             print($msg."\n");

}
// Create socket
$sock = socket_create(AF_INET,SOCK_STREAM,0) or die("[".date('Y-m-d H:i:s')."] Could not create socket\n");
// Bind to socket
socket_bind($sock,$host,$port) or die("[".date('Y-m-d H:i:s')."] Could not bind to socket\n");
// Start listening
socket_listen($sock) or die("[".date('Y-m-d H:i:s')."] Could not set up socket listener\n");

rLog("Server started at ".$host.":".$port);
// Server loop
while(true){
             socket_set_block($sock);
             // Setup clients listen socket for reading
             $read[0] = $sock;
             for($i = 0;$i<$max;$i++){
                          if($client[$i]['sock'] != null)
                                       $read[$i+1] = $client[$i]['sock'];
             }
             // Set up a blocking call to socket_select()
             $ready = socket_select($read,$write = NULL, $except = NULL, $tv_sec = NULL);
             // If a new connection is being made add it to the clients array
             if(in_array($sock,$read)){
                          for($i = 0;$i<$max;$i++){
                                       if($client[$i]['sock']==null){
                                                    if(($client[$i]['sock'] = socket_accept($sock))<0){
                                                                 rLog("socket_accept() failed: ".socket_strerror($client[$i]['sock']));
                                                    }else{
                                                                 rLog("Client #".$i." connected");
                                                    }
                                                    break;
                                       }elseif($i == $max - 1){
                                                    rLog("Too many clients");
                                       }
                          }
                          if(--$ready <= 0)
                          continue;
             }
             for($i=0;$i<$max;$i++){
                          if(in_array($client[$i]['sock'],$read)){
                                       $input = socket_read($client[$i]['sock'],1024);
                                       if($input==null){
                                                    unset($client[$i]);
                                       }
                                       $n = trim($input);
                                       $com = split(" ",$n);
                                       if($n=="EXIT"){
                                                    if($client[$i]['sock']!=null){
                                                                 // Disconnect requested
                                                                 socket_close($client[$i]['sock']);
                                                                 unset($client[$i]['sock']);
                                                                 rLog("Disconnected(2) client #".$i);
                                                                 for($p=0;$p<count($client);$p++){
                                                                              socket_write($client[$p]['sock'],"DISC ".$i.chr(0));
                                                                 }
                                                                 if($i == $adm){
                                                                              $adm = -1;
                                                                 }
                                                    }
                                       }elseif($n=="TERM"){
                                                    // Server termination requested
                                                    socket_close($sock);
                                                    rLog("Terminated server (requested by client #".$i.")");
                                                    exit();
                                       }elseif($input){
                                                    // Strip whitespaces and write back to user
                                                    // Respond to commands
                                                    /*$output = ereg_replace("[ \t\n\r]","",$input).chr(0);
                                                    socket_write($client[$i]['sock'],$output);*/
                                                    if($n=="PING"){
                                                                 socket_write($client[$i]['sock'],"PONG".chr(0));
                                                    }
                                                    if($n=="<policy-file-request/>"){
                                                                 rLog("Client #".$i." requested a policy file...");
                                                                 $cdmp="<?xml version=\"1.0\" encoding=\"UTF-8\"?><cross-domain-policy xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:noNamespaceSchemaLocation=\"http://www.adobe.com/xml/schemas/PolicyFileSocket.xsd\"><allow-access-from domain=\"*\" to-ports=\"*\" secure=\"false\" /><site-control permitted-cross-domain-policies=\"master-only\" /></cross-domain-policy>";
                                                                 socket_write($client[$i]['sock'],$cdmp.chr(0));
                                                                 socket_close($client[$i]['sock']);
                                                                 unset($client[$i]);
                                                                 $cdmp="";
                                                    }
                                       }
                          }else{
                                       //if($client[$i]['sock']!=null){
                                                    // Close the socket
                                                    //socket_close($client[$i]['sock']);
                                                    //unset($client[$i]);
                                                    //rLog("Disconnected(1) client #".$i);
                                       //}
                          }
             }
}
// Close the master sockets
socket_close($sock);
?>

Basically this is a functioning socket server (execute it via PHPs CLI) but to actually do something with it requires some minor modifications. One easy modification you can do, is create a command to send a message to all other clients;

...if($n=="PING"){
        socket_write($client[$i]['sock'],"PONG".chr(0));
 }

You can already use this script with Flash, but only locally. I will soon write how to properly prepare this server for Flash (e.g. make it send policy files) and how to use it with flash. And for those who cannot wait for another post please remember that you cannot test your ‘internet’ (so not local) connecting flash client on the same PC as your PHP server.