PHP Sockets - Accept multiple connections - php

Question

I'm trying to create a simple client/server application and thus I am experimenting with sockets in PHP.
Now I have a simple client in C# which connects to the server well, but i can only connect one client at once to this server (I found this code sample online and tweaked it a bit for testing purposes).
Funny enough I found the same question, based on the same example here: https://stackoverflow.com/questions/10318023/php-socket-connections-cant-handle-multiple-connection
I tried to understand every part of it and I'm close to seeing how it works in detail, but for some reason, when I connect a 2nd client, the first one gets disconnected / crashes.
Can anyone give me some wild ideas or a pointer to where I should look at?
<?php
// Set time limit to indefinite execution
set_time_limit (0);
// Set the ip and port we will listen on
$address = '127.0.0.1';
$port = 9000;
$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);
// Loop continuously
while (true) {
// Setup clients listen socket for reading
$read[0] = $sock;
for ($i = 0; $i < $max_clients; $i++)
{
if (isset($client[$i]))
if ($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, $tv_sec = NULL);
/* if a new connection is being made add it to the client array */
if (in_array($sock, $read)) {
for ($i = 0; $i < $max_clients; $i++)
{
if (!isset($client[$i])) {
$client[$i] = array();
$client[$i]['sock'] = socket_accept($sock);
echo("Accepting incoming connection...\n");
break;
}
elseif ($i == $max_clients - 1)
print ("too many clients");
}
if (--$ready <= 0)
continue;
} // 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[$i]))
if (in_array($client[$i]['sock'] , $read))
{
$input = socket_read($client[$i]['sock'] , 1024);
if ($input == null) {
// Zero length string meaning disconnected
echo("Client disconnected\n");
unset($client[$i]);
}
$n = trim($input);
if ($n == 'exit') {
echo("Client requested disconnect\n");
// requested disconnect
socket_close($client[$i]['sock']);
}
if(substr($n,0,3) == 'say') {
//broadcast
echo("Broadcast received\n");
for ($j = 0; $j < $max_clients; $j++) // for each client
{
if (isset($client[$j]))
if ($client[$j]['sock']) {
socket_write($client[$j]['sock'], substr($n, 4, strlen($n)-4).chr(0));
}
}
} elseif ($input) {
echo("Returning stripped input\n");
// strip white spaces and write back to user
$output = ereg_replace("[ \t\n\r]","",$input).chr(0);
socket_write($client[$i]['sock'],$output);
}
} else {
// Close the socket
if (isset($client[$i]))
echo("Client disconnected\n");
if ($client[$i]['sock'] != null){
socket_close($client[$i]['sock']);
unset($client[$i]);
}
}
}
} // end while
// Close the master sockets
echo("Shutting down\n");
socket_close($sock);
?>

Answer 1

The current top answer here is wrong, you don't need multiple threads to handle multiple clients. You can use non-blocking I/O and stream_select / socket_select to process messages from clients that are actionable. I'd recommend using the stream_socket_* functions over socket_*.
While non-blocking I/O works quite fine, you can't make any function calls with involve blocking I/O, otherwise that blocking I/O blocks the complete process and all clients hang, not just one.
That means all I/O has to be non-blocking or guaranteed to be very fast (which isn't perfect, but might be acceptable). Because not only your sockets need to use stream_select, but you need to select on all open streams, I'd recommend a library that offers to register read and write watchers that are executed once a stream becomes readable / writable.
There are multiple such frameworks available, the most common ones are ReactPHP and Amp. The underlying event loops are pretty similar, but Amp offers a few more features on that side.
The main difference between the two is the approach for APIs. While ReactPHP uses callbacks everywhere, Amp tries to avoid them by using coroutines and optimizing its APIs for such a usage.
Amp's "Getting Started" guide is basically exactly about this topic. You can read the full guide here. I'll include a working example below.
<?php
require __DIR__ . "/vendor/autoload.php";
// Non-blocking server implementation based on amphp/socket.
use Amp\Loop;
use Amp\Socket\ServerSocket;
use function Amp\asyncCall;
Loop::run(function () {
$uri = "tcp://127.0.0.1:1337";
$clientHandler = function (ServerSocket $socket) {
while (null !== $chunk = yield $socket->read()) {
yield $socket->write($chunk);
}
};
$server = Amp\Socket\listen($uri);
while ($socket = yield $server->accept()) {
asyncCall($clientHandler, $socket);
}
});
Loop::run() runs the event loop and watches for timer events, signals and actionable streams, which can be registered with Loop::on*() methods. A server socket is created using Amp\Socket\listen(). Server::accept() returns a Promise which can be used to await new client connections. It executes a coroutine once a client is accepted that reads from the client and echo's the same data back to it. For more details, refer to Amp's documentation.

Answer 2

This script is working perfectly for me
<?php
/*! #class SocketServer
#author Navarr Barnier
#abstract A Framework for creating a multi-client server using the PHP language.
*/
class SocketServer
{
/*! #var config
#abstract Array - an array of configuration information used by the server.
*/
protected $config;
/*! #var hooks
#abstract Array - a dictionary of hooks and the callbacks attached to them.
*/
protected $hooks;
/*! #var master_socket
#abstract resource - The master socket used by the server.
*/
protected $master_socket;
/*! #var max_clients
#abstract unsigned int - The maximum number of clients allowed to connect.
*/
public $max_clients = 10;
/*! #var max_read
#abstract unsigned int - The maximum number of bytes to read from a socket at a single time.
*/
public $max_read = 1024;
/*! #var clients
#abstract Array - an array of connected clients.
*/
public $clients;
/*! #function __construct
#abstract Creates the socket and starts listening to it.
#param string - IP Address to bind to, NULL for default.
#param int - Port to bind to
#result void
*/
public function __construct($bind_ip,$port)
{
set_time_limit(0);
$this->hooks = array();
$this->config["ip"] = $bind_ip;
$this->config["port"] = $port;
$this->master_socket = socket_create(AF_INET, SOCK_STREAM, 0);
socket_bind($this->master_socket,$this->config["ip"],$this->config["port"]) or die("Issue Binding");
socket_getsockname($this->master_socket,$bind_ip,$port);
socket_listen($this->master_socket);
SocketServer::debug("Listenting for connections on {$bind_ip}:{$port}");
}
/*! #function hook
#abstract Adds a function to be called whenever a certain action happens. Can be extended in your implementation.
#param string - Command
#param callback- Function to Call.
#see unhook
#see trigger_hooks
#result void
*/
public function hook($command,$function)
{
$command = strtoupper($command);
if(!isset($this->hooks[$command])) { $this->hooks[$command] = array(); }
$k = array_search($function,$this->hooks[$command]);
if($k === FALSE)
{
$this->hooks[$command][] = $function;
}
}
/*! #function unhook
#abstract Deletes a function from the call list for a certain action. Can be extended in your implementation.
#param string - Command
#param callback- Function to Delete from Call List
#see hook
#see trigger_hooks
#result void
*/
public function unhook($command = NULL,$function)
{
$command = strtoupper($command);
if($command !== NULL)
{
$k = array_search($function,$this->hooks[$command]);
if($k !== FALSE)
{
unset($this->hooks[$command][$k]);
}
} else {
$k = array_search($this->user_funcs,$function);
if($k !== FALSE)
{
unset($this->user_funcs[$k]);
}
}
}
/*! #function loop_once
#abstract Runs the class's actions once.
#discussion Should only be used if you want to run additional checks during server operation. Otherwise, use infinite_loop()
#param void
#see infinite_loop
#result bool - True
*/
public function loop_once()
{
// Setup Clients Listen Socket For Reading
$read[0] = $this->master_socket;
for($i = 0; $i < $this->max_clients; $i++)
{
if(isset($this->clients[$i]))
{
$read[$i + 1] = $this->clients[$i]->socket;
}
}
// Set up a blocking call to socket_select
if(socket_select($read,$write = NULL, $except = NULL, $tv_sec = 5) < 1)
{
// SocketServer::debug("Problem blocking socket_select?");
return true;
}
// Handle new Connections
if(in_array($this->master_socket, $read))
{
for($i = 0; $i < $this->max_clients; $i++)
{
if(empty($this->clients[$i]))
{
$temp_sock = $this->master_socket;
$this->clients[$i] = new SocketServerClient($this->master_socket,$i);
$this->trigger_hooks("CONNECT",$this->clients[$i],"");
break;
}
elseif($i == ($this->max_clients-1))
{
SocketServer::debug("Too many clients... :( ");
}
}
}
// Handle Input
for($i = 0; $i < $this->max_clients; $i++) // for each client
{
if(isset($this->clients[$i]))
{
if(in_array($this->clients[$i]->socket, $read))
{
$input = socket_read($this->clients[$i]->socket, $this->max_read);
if($input == null)
{
$this->disconnect($i);
}
else
{
SocketServer::debug("{$i}#{$this->clients[$i]->ip} --> {$input}");
$this->trigger_hooks("INPUT",$this->clients[$i],$input);
}
}
}
}
return true;
}
/*! #function disconnect
#abstract Disconnects a client from the server.
#param int - Index of the client to disconnect.
#param string - Message to send to the hooks
#result void
*/
public function disconnect($client_index,$message = "")
{
$i = $client_index;
SocketServer::debug("Client {$i} from {$this->clients[$i]->ip} Disconnecting");
$this->trigger_hooks("DISCONNECT",$this->clients[$i],$message);
$this->clients[$i]->destroy();
unset($this->clients[$i]);
}
/*! #function trigger_hooks
#abstract Triggers Hooks for a certain command.
#param string - Command who's hooks you want to trigger.
#param object - The client who activated this command.
#param string - The input from the client, or a message to be sent to the hooks.
#result void
*/
public function trigger_hooks($command,&$client,$input)
{
if(isset($this->hooks[$command]))
{
foreach($this->hooks[$command] as $function)
{
SocketServer::debug("Triggering Hook '{$function}' for '{$command}'");
$continue = call_user_func($function,&$this,&$client,$input);
if($continue === FALSE) { break; }
}
}
}
/*! #function infinite_loop
#abstract Runs the server code until the server is shut down.
#see loop_once
#param void
#result void
*/
public function infinite_loop()
{
$test = true;
do
{
$test = $this->loop_once();
}
while($test);
}
/*! #function debug
#static
#abstract Outputs Text directly.
#discussion Yeah, should probably make a way to turn this off.
#param string - Text to Output
#result void
*/
public static function debug($text)
{
echo("{$text}\r\n");
}
/*! #function socket_write_smart
#static
#abstract Writes data to the socket, including the length of the data, and ends it with a CRLF unless specified.
#discussion It is perfectly valid for socket_write_smart to return zero which means no bytes have been written. Be sure to use the === operator to check for FALSE in case of an error.
#param resource- Socket Instance
#param string - Data to write to the socket.
#param string - Data to end the line with. Specify a "" if you don't want a line end sent.
#result mixed - Returns the number of bytes successfully written to the socket or FALSE on failure. The error code can be retrieved with socket_last_error(). This code may be passed to socket_strerror() to get a textual explanation of the error.
*/
public static function socket_write_smart(&$sock,$string,$crlf = "\r\n")
{
SocketServer::debug("<-- {$string}");
if($crlf) { $string = "{$string}{$crlf}"; }
return socket_write($sock,$string,strlen($string));
}
/*! #function __get
#abstract Magic Method used for allowing the reading of protected variables.
#discussion You never need to use this method, simply calling $server->variable works because of this method's existence.
#param string - Variable to retrieve
#result mixed - Returns the reference to the variable called.
*/
function &__get($name)
{
return $this->{$name};
}
}
/*! #class SocketServerClient
#author Navarr Barnier
#abstract A Client Instance for use with SocketServer
*/
class SocketServerClient
{
/*! #var socket
#abstract resource - The client's socket resource, for sending and receiving data with.
*/
protected $socket;
/*! #var ip
#abstract string - The client's IP address, as seen by the server.
*/
protected $ip;
/*! #var hostname
#abstract string - The client's hostname, as seen by the server.
#discussion This variable is only set after calling lookup_hostname, as hostname lookups can take up a decent amount of time.
#see lookup_hostname
*/
protected $hostname;
/*! #var server_clients_index
#abstract int - The index of this client in the SocketServer's client array.
*/
protected $server_clients_index;
/*! #function __construct
#param resource- The resource of the socket the client is connecting by, generally the master socket.
#param int - The Index in the Server's client array.
#result void
*/
public function __construct(&$socket,$i)
{
$this->server_clients_index = $i;
$this->socket = socket_accept($socket) or die("Failed to Accept");
SocketServer::debug("New Client Connected");
socket_getpeername($this->socket,$ip);
$this->ip = $ip;
}
/*! #function lookup_hostname
#abstract Searches for the user's hostname and stores the result to hostname.
#see hostname
#param void
#result string - The hostname on success or the IP address on failure.
*/
public function lookup_hostname()
{
$this->hostname = gethostbyaddr($this->ip);
return $this->hostname;
}
/*! #function destroy
#abstract Closes the socket. Thats pretty much it.
#param void
#result void
*/
public function destroy()
{
socket_close($this->socket);
}
function &__get($name)
{
return $this->{$name};
}
function __isset($name)
{
return isset($this->{$name});
}
}
Source on github

Answer 3

Typically socket servers need to be multi-threaded if you want to handle > 1 client. You'd create a 'listen' thread and spawn a new 'answer' thread for each client request. Im not sure how PHP would handle a situation like this though. Perhaps it has a fork mechanism?
EDIT: Doesn't appear that PHP offers threading per se (http://stackoverflow.com/questions/70855/how-can-one-use-multi-threading-in-php-applications) If you want to follow the typical paradigm for a socket server you might get away with using 'popen' to spawn a process to handle the child request. Hand off the socket id and let it close itself when the child socket closes. You'd need to keep on top of this list to avoid orphaning these processes if your server process closes.
FWIW: here are some examples of multi-client servers: http://php.net/manual/en/function.socket-accept.php

Answer 4

I found this online. but I would like to share this code on here. as I don't find else where.
<?php
// port number
$port = 5000;
// IP address
$address = '127.0.0.1';
// Maximum client number
$max_clients_number = 10;
// Create master stream sockets.
$master_stream_socket = socket_create(AF_INET, SOCK_STREAM, 0);
// Bind the socket to IP address and Port number.
socket_bind($master_stream_socket, $address, $port);
// Start to listen for the client.
socket_listen($master_stream_socket);
// This variable will hold client informations.
$clients = [$master_stream_socket];
while(true){
$read = $clients;
if( socket_select($read, $write = null, $exp = null, null) ){
if( in_array( $master_stream_socket, $read ) ){
$c_socket = socket_accept($master_stream_socket);
$clients[] = $c_socket;
$key = array_search($master_stream_socket, $read);
unset( $read[ $key ] );
}
if( count($read) > 0 ) {
foreach( $read as $current_socket ) {
$content = socket_read($current_socket, 2048);
foreach( $clients as $client ) {
if( $client != $master_stream_socket && $client != $current_socket ){
socket_write($client, $content, strlen($content));
}
}
}
}
} else {
continue;
}
}
// Close master sockets.
socket_close($master_stream_socket);
?>

Answer 5

Check This
git clone https://github.com/lukaszkujawa/php-multithreaded-socket-server.git socketserver
cd socketserver
php server.php
for more information go to: http://systemsarchitect.net/multi-threaded-socket-server-in-php-with-fork/