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Few years back HTML5 opened WebSocket technology, now we can use WebSockets using javascript. A secure version of the WebSocket protocol is implemented in Firefox version 6, Google Chrome version 14, Opera version 12.10 and Internet Explorer version 10.
WebSocket connection has following steps
1. Client try to connect to WebSocket server
2. Server recognize client
3. If client is not registered with server then add client (this is known as handshaking process which is based on headers transmission)
4. Send and receive data
5. Close connection
WebSocket protocol handshake
This very important step to establish a WebSocket connection, client sends a WebSocket handshake request, and the server sends a WebSocket handshake response, as shown in the following example:
Request headers from client
GET /mychat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Protocol: chat
Sec-WebSocket-Version: 13
Origin: http://example.com
Response headers from server
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat
The client sends a Sec-WebSocket-Key which is base64 encoded. To form a response, the magic string 258EAFA5-E914-47DA-95CA-C5AB0DC85B11 is appended to this (undecoded) key. The resulting string is then hashed with SHA-1, then base64 encoded. Finally, the resulting reply occurs in the header Sec-WebSocket-Accept.
Set up your own PHP socket server
Code:
<?php /* >php -q server.php */
error_reporting(E_ALL);
set_time_limit(0);
ob_implicit_flush();
$address = "127.0.0.1";
$port = "1222";
GLOBAL $clients;
GLOBAL $client_list;
// socket creation
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_option($socket, SOL_SOCKET, SO_REUSEADDR, 1);
if (!is_resource($socket))
console("socket_create() failed: ".socket_strerror(socket_last_error()), true);
if (!socket_bind($socket, $address, $port))
console("socket_bind() failed: ".socket_strerror(socket_last_error()), true);
if(!socket_listen($socket, 20))
console("socket_listen() failed: ".socket_strerror(socket_last_error()), true);
console("Server started on $address : $port\n\n");
$master = $socket;
$sockets = array($socket);
while(true){
$changed = $sockets;
foreach($changed as $socket){
if($socket==$master){
// new client will enter in this case and connect with server
socket_select($changed,$write=NULL,$except=NULL,NULL);
console("Master Socket Changed.\n\n");
$client=socket_accept($master);
if($client<0)
{ console("socket_accept() failed\n\n"); continue; }
else
{ console("Connecting socket.\n\n"); fnConnectacceptedSocket($socket,$client); $master=null; }
}else{
// clients who are connected with server will enter into this case
// first client will handshake with server and then exchange data with server
$client = getClientBySocket($socket);
if($client) {
if ($clients[$socket]["handshake"] == false){
$bytes = @socket_recv($client, $data, 2048, MSG_DONTWAIT);
if ((int)$bytes == 0)
continue;
console("Handshaking headers from client:".$data);
if (handshake($client, $data, $socket))
$clients[$socket]["handshake"] = true;
} else if ($clients[$socket]["handshake"] == true){
$bytes = @socket_recv($client, $data, 2048, MSG_DONTWAIT);
if ($data != ""){
$decoded_data = unmask($data);
socket_write($client, encode("You have entered: ".$decoded_data));
console("Data from client:".$decoded_data);
socket_close($socket);
}
}
}
}
}
}
# Close the master sockets
socket_close($socket);
function unmask($payload) {
$length = ord($payload[1]) & 127;
if($length == 126) {
$masks = substr($payload, 4, 4);
$data = substr($payload, 8);
}
elseif($length == 127) {
$masks = substr($payload, 10, 4);
$data = substr($payload, 14);
}
else {
$masks = substr($payload, 2, 4);
$data = substr($payload, 6);
}
$text = '';
for ($i = 0; $i < strlen($data); ++$i) {
$text .= $data[$i] ^ $masks[$i%4];
}
return $text;
}
function encode($text)
{
// 0x1 text frame (FIN + opcode)
$b1 = 0x80 | (0x1 & 0x0f);
$length = strlen($text);
if($length <= 125) $header = pack('CC', $b1, $length); elseif($length > 125 && $length < 65536) $header = pack('CCS', $b1, 126, $length); elseif($length >= 65536)
$header = pack('CCN', $b1, 127, $length);
return $header.$text;
}
function fnConnectacceptedSocket($socket,$client) {
GLOBAL $clients;
GLOBAL $client_list;
$clients[$socket]["id"] = uniqid();
$clients[$socket]["socket"] = $socket;
$clients[$socket]["handshake"] = false;
console("Accepted client \n\n");
$client_list[$socket] = $client;
}
function getClientBySocket($socket) {
GLOBAL $client_list;
return $client_list[$socket];
}
function handshake($client, $headers, $socket) {
if(preg_match("/Sec-WebSocket-Version: (.*)\r\n/", $headers, $match))
$version = $match[1];
else {
console("The client doesn't support WebSocket");
return false;
}
if($version == 13) {
// Extract header variables
if(preg_match("/GET (.*) HTTP/", $headers, $match))
$root = $match[1];
if(preg_match("/Host: (.*)\r\n/", $headers, $match))
$host = $match[1];
if(preg_match("/Origin: (.*)\r\n/", $headers, $match))
$origin = $match[1];
if(preg_match("/Sec-WebSocket-Key: (.*)\r\n/", $headers, $match))
$key = $match[1];
$acceptKey = $key.'258EAFA5-E914-47DA-95CA-C5AB0DC85B11';
$acceptKey = base64_encode(sha1($acceptKey, true));
$upgrade = "HTTP/1.1 101 Switching Protocols\r\n".
"Upgrade: websocket\r\n".
"Connection: Upgrade\r\n".
"Sec-WebSocket-Accept: $acceptKey".
"\r\n\r\n";
socket_write($client, $upgrade);
return true;
}
else {
console("WebSocket version 13 required (the client supports version {$version})");
return false;
}
}
function console($text){
$File = "log.txt";
$Handle = fopen($File, 'a');
fwrite($Handle, $text);
fclose($Handle);
}
?>
Copy above code and create PHP file socket_server.php
Test socket server with HTML5 client
<html>
<head>
<title>WebSocket</title>
<style>
html,body{font:normal 0.9em arial,helvetica;}
#log {width:440px; height:200px; border:1px solid #7F9DB9; overflow:auto;}
#msg {width:330px;}
</style>
<script>
var socket;
function init(){
var host = "ws://127.0.0.1:1222";
try{
socket = new WebSocket(host);
log('WebSocket - status '+socket.readyState);
socket.onopen = function(msg){ log("Welcome - status "+this.readyState); };
socket.onmessage = function(msg){ log("Received: "+msg.data); };
socket.onclose = function(msg){ log("Disconnected - status "+this.readyState); };
}
catch(ex){ log(ex); }
$("msg").focus();
}
function send(){
var txt,msg;
txt = $("msg");
msg = txt.value;
if(!msg){ alert("Message can not be empty"); return; }
txt.value="";
txt.focus();
try{ socket.send(msg); log('Sent: '+msg); } catch(ex){ log(ex); }
}
function quit(){
log("Goodbye!");
socket.close();
socket=null;
}
// Utilities
function $(id){ return document.getElementById(id); }
function log(msg){ $("log").innerHTML+="\n"+msg; }
function onkey(event){ if(event.keyCode==13){ send(); } }
</script>
</head>
<body onload="init()">
<h3>WebSocket v2.00</h3>
<div id="log"></div>
<input id="msg" type="textbox" onkeypress="onkey(event)"/>
<button onclick="send()">Send</button>
<button onclick="quit()">Quit</button>
<div>Commands: hello, hi, name, age, date, time, thanks, bye</div>
</body>
</html>
Code:
nohup php -q socket_server.php &
You are all set to use you PHP socket server.
Source: Cuelogic Blog