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How to implement Socket server with PHP_PHP tutorial
- WBOYOriginal
- 2016-07-13 09:46:57866browse
How to implement Socket server with PHP
Want to build a chat app, or even a game? Then, the socket server will be your first step. Once you understand the basic functionality of creating a server, subsequent optimization steps become equally simple.
The socket server works like this, running continuously to wait for client connections. Once the client is connected, the server adds it to the client list and starts waiting for messages from the client.
Don’t go away, here is the complete source code:
<ol class="dp-j"><li class="alt"><span><span class="comment">// Set time limit to indefinite execution</span><span> </span></span></li><li><span>set_time_limit (<span class="number">0</span><span>); </span></span></li><li class="alt"><span> </span></li><li><span><span class="comment">// Set the ip and port we will listen on</span><span> </span></span></li><li class="alt"><span>$address = <span class="string">'localhost'</span><span>; </span></span></li><li><span>$port = <span class="number">10000</span><span>; </span></span></li><li class="alt"><span>$max_clients = <span class="number">10</span><span>; </span></span></li><li><span> </span></li><li class="alt"><span><span class="comment">// Array that will hold client information</span><span> </span></span></li><li><span>$client = Array(); </span></li><li class="alt"><span> </span></li><li><span><span class="comment">// Create a TCP Stream socket</span><span> </span></span></li><li class="alt"><span>$sock = socket_create(AF_INET, SOCK_STREAM, <span class="number">0</span><span>); </span></span></li><li><span><span class="comment">// Bind the socket to an address/port</span><span> </span></span></li><li class="alt"><span>socket_bind($sock, $address, $port) or die(<span class="string">'Could not bind to address'</span><span>); </span></span></li><li><span><span class="comment">// Start listening for connections</span><span> </span></span></li><li class="alt"><span>socket_listen($sock); </span></li><li><span> </span></li><li class="alt"><span>echo <span class="string">"Waiting for connections...\r\n"</span><span>; </span></span></li><li><span> </span></li><li class="alt"><span><span class="comment">// Loop continuously</span><span> </span></span></li><li><span><span class="keyword">while</span><span> (</span><span class="keyword">true</span><span>) { </span></span></li><li class="alt"><span><span class="comment">// Setup clients listen socket for reading</span><span> </span></span></li><li><span>$read[<span class="number">0</span><span>] = $sock; </span></span></li><li class="alt"><span><span class="keyword">for</span><span> ($i = </span><span class="number">0</span><span>; $i < $max_clients; $i++) { </span></span></li><li><span> <span class="keyword">if</span><span> (isset($client[$i][</span><span class="string">'sock'</span><span>])) </span></span></li><li class="alt"><span> $read[$i + <span class="number">1</span><span>] = $client[$i][</span><span class="string">'sock'</span><span>]; </span></span></li><li><span>} </span></li><li class="alt"><span><span class="comment">// Set up a blocking call to socket_select()</span><span> </span></span></li><li><span><span class="keyword">if</span><span> (socket_select($read, $write = NULL, $except = NULL, $tv_sec = </span><span class="number">5</span><span>) < </span><span class="number">1</span><span>) </span></span></li><li class="alt"><span> <span class="keyword">continue</span><span>; </span></span></li><li><span><span class="comment">/* if a new connection is being made add it to the client array */</span><span> </span></span></li><li class="alt"><span><span class="keyword">if</span><span> (in_array($sock, $read)) { </span></span></li><li><span> <span class="keyword">for</span><span> ($i = </span><span class="number">0</span><span>; $i < $max_clients; $i++) { </span></span></li><li class="alt"><span> <span class="keyword">if</span><span> (empty($client[$i][</span><span class="string">'sock'</span><span>])) { </span></span></li><li><span> $client[$i][<span class="string">'sock'</span><span>] = socket_accept($sock); </span></span></li><li class="alt"><span> echo <span class="string">"New client connected $i\r\n"</span><span>; </span></span></li><li><span> <span class="keyword">break</span><span>; </span></span></li><li class="alt"><span> } </span></li><li><span> elseif ($i == $max_clients - <span class="number">1</span><span>) </span></span></li><li class="alt"><span> echo <span class="string">"Too many clients...\r\n"</span><span>; </span></span></li><li><span> } </span></li><li class="alt"><span>} <span class="comment">// end if in_array</span><span> </span></span></li><li><span> </span></li><li class="alt"><span><span class="comment">// If a client is trying to write - handle it now</span><span> </span></span></li><li><span><span class="keyword">for</span><span> ($i = </span><span class="number">0</span><span>; $i < $max_clients; $i++) { </span><span class="comment">// for each client</span><span> </span></span></li><li class="alt"><span> <span class="keyword">if</span><span> (isset($client[$i][</span><span class="string">'sock'</span><span>])) { </span></span></li><li><span> <span class="keyword">if</span><span> (in_array($client[$i][</span><span class="string">'sock'</span><span>], $read)) { </span></span></li><li class="alt"><span> $input = socket_read($client[$i][<span class="string">'sock'</span><span>], </span><span class="number">1024</span><span>); </span></span></li><li><span> <span class="keyword">if</span><span> ($input == </span><span class="keyword">null</span><span>) { </span></span></li><li class="alt"><span> echo <span class="string">"Client disconnecting $i\r\n"</span><span>; </span></span></li><li><span> <span class="comment">// Zero length string meaning disconnected</span><span> </span></span></li><li class="alt"><span> unset($client[$i]); </span></li><li><span> } <span class="keyword">else</span><span> { </span></span></li><li class="alt"><span> echo <span class="string">"New input received $i\r\n"</span><span>; </span></span></li><li><span> <span class="comment">// send it to the other clients</span><span> </span></span></li><li class="alt"><span> <span class="keyword">for</span><span> ($j = </span><span class="number">0</span><span>; $j < $max_clients; $j++) { </span></span></li><li><span> <span class="keyword">if</span><span> (isset($client[$j][</span><span class="string">'sock'</span><span>]) && $j != $i) { </span></span></li><li class="alt"><span> echo <span class="string">"Writing '$input' to client $j\r\n"</span><span>; </span></span></li><li><span> socket_write($client[$j][<span class="string">'sock'</span><span>], $input, strlen($input)); </span></span></li><li class="alt"><span> } </span></li><li><span> } </span></li><li class="alt"><span> <span class="keyword">if</span><span> ($input == </span><span class="string">'exit'</span><span>) { </span></span></li><li><span> <span class="comment">// requested disconnect</span><span> </span></span></li><li class="alt"><span> socket_close($client[$i][<span class="string">'sock'</span><span>]); </span></span></li><li><span> } </span></li><li class="alt"><span> } </span></li><li><span> } <span class="keyword">else</span><span> { </span></span></li><li class="alt"><span> echo <span class="string">"Client disconnected $i\r\n"</span><span>; </span></span></li><li><span> <span class="comment">// Close the socket</span><span> </span></span></li><li class="alt"><span> socket_close($client[$i][<span class="string">'sock'</span><span>]); </span></span></li><li><span> unset($client[$i]); </span></li><li class="alt"><span> } </span></li><li><span> } </span></li><li class="alt"><span>} </span></li><li><span>} <span class="comment">// end while</span><span> </span></span></li><li class="alt"><span><span class="comment">// Close the master sockets</span><span> </span></span></li><li><span>socket_close($sock); </span></li></ol>
Gee, this may seem like a big project at first, but we can start by breaking it down into smaller parts. The first part is creating the server. Lines: 2 to 20.
This part of the code sets the variables, address, port, maximum client and client array. Next create the socket and bind it to the address and port we specified.
What we have to do next is to execute an infinite loop. In fact, we did it on purpose! ). Lines: 22 to 32. The first step we do in this part of the code is to set up the $read array. This array contains all the client's sockets and our main server's sockets. This variable will be used later in the select statement: telling PHP to listen for every message from these clients.
The last parameter of socket_select() tells our server to wait up to 5 seconds before returning a value. If its return value is less than 1, it means that no data has been received, so you just need to return to the top of the loop and continue waiting.
The next part of the script is to add a new client to the array. Lines: 33 to 44.
Place the new client at the end of the list. Check to make sure we don't have more clients than we want the server to handle.
The code block to be described below is quite large and is a major part of the server. When the client sends a message to the server, this piece of code needs to come forward to process it. The message can be anything from a disconnect message to an actual disconnect - whatever the server needs to process. Lines: 46 to the end.
The code loops through each client and checks if a message has been received from them. If so, get the input content. Check based on the input whether this is a disconnect message, if so then delete them from the array, otherwise, then it is a normal message, then our server goes through all the clients again and writes the message to them one by one, Skip sender.
Okay, let’s try creating your own chat server!
