How to implement Socket server using PHP_php tips

The socket server works like this, running continuously to wait for client connections. Once the client connects, 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:

// Set time limit to indefinite execution 
set_time_limit (0); 
 
// Set the ip and port we will listen on 
$address = 'localhost'; 
$port = 10000; 
$max_clients = 10; 
 
// Array that will hold client information 
$client = Array(); 
 
// Create a TCP Stream socket 
$sock = socket_create(AF_INET, SOCK_STREAM, 0); 
// Bind the socket to an address/port 
socket_bind($sock, $address, $port) or die('Could not bind to address'); 
// Start listening for connections 
socket_listen($sock); 
 
echo "Waiting for connections...\r\n"; 
 
// Loop continuously 
while (true) { 
// Setup clients listen socket for reading 
$read[0] = $sock; 
for ($i = 0; $i < $max_clients; $i++) { 
 if (isset($client[$i]['sock'])) 
  $read[$i + 1] = $client[$i]['sock']; 
} 
// Set up a blocking call to socket_select() 
if (socket_select($read, $write = NULL, $except = NULL, $tv_sec = 5) < 1) 
 continue; 
/* if a new connection is being made add it to the client array */ 
if (in_array($sock, $read)) { 
 for ($i = 0; $i < $max_clients; $i++) { 
  if (empty($client[$i]['sock'])) { 
  $client[$i]['sock'] = socket_accept($sock); 
  echo "New client connected $i\r\n"; 
  break; 
  } 
  elseif ($i == $max_clients - 1) 
  echo "Too many clients...\r\n"; 
 } 
} // end if in_array 
 
// If a client is trying to write - handle it now 
for ($i = 0; $i < $max_clients; $i++) { // for each client 
 if (isset($client[$i]['sock'])) { 
  if (in_array($client[$i]['sock'], $read)) { 
  $input = socket_read($client[$i]['sock'], 1024); 
  if ($input == null) { 
   echo "Client disconnecting $i\r\n"; 
   // Zero length string meaning disconnected 
   unset($client[$i]); 
  } else { 
   echo "New input received $i\r\n"; 
   // send it to the other clients 
   for ($j = 0; $j < $max_clients; $j++) { 
   if (isset($client[$j]['sock']) && $j != $i) { 
    echo "Writing '$input' to client $j\r\n"; 
    socket_write($client[$j]['sock'], $input, strlen($input)); 
   } 
   } 
   if ($input == 'exit') { 
   // requested disconnect 
   socket_close($client[$i]['sock']); 
   } 
  } 
  } else { 
  echo "Client disconnected $i\r\n"; 
  // Close the socket 
  socket_close($client[$i]['sock']); 
  unset($client[$i]); 
  } 
 } 
} 
} // end while 
// Close the master sockets 
socket_close($sock); 

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 to create 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 (actually 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 the 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 introduced below is quite large and is the main 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 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!