connect multiple device android to the same php socket - php

Question

My problem is when I try to connect the Android application with Java socket identified by an IP and a port 4444 with a PHP service, identified by the same port, and keep this connection open to accept multiple connections via the Android app.
So with a second Android device if we connect to PHP we will have the same communication channel as the one device and we cannot identify which device is connected via PHP.
Is there a possibility to differentiate these two connections via the PHP file or instantiate two different PHP service for the two devices.
The Android code:
public String connect() {
Socket socket = null;
try {
socket = new Socket();
// This limits the time allowed to establish a connection in the case
// that the connection is refused or server doesn't exist.
socket.connect(new InetSocketAddress(dstAddress, dstPort), context.getResources().getInteger(R.integer.time_out));
// This stops the request from dragging on after connection succeeds.
socket.setSoTimeout(context.getResources().getInteger(R.integer.time_out));
// socket = new Socket();
// socket.connect(new InetSocketAddress(dstAddress, dstPort), 2000);
if (!socket.isConnected())
throw new SocketException("Could not connect to Socket");
DataInputStream DIStream = new DataInputStream(socket.getInputStream());
DataOutputStream DOStream = new DataOutputStream(socket.getOutputStream());
DOStream.write(numCmd.getBytes(), 0, numCmd.getBytes().length);
DOStream.flush();
response = DIStream.readLine();
DOStream.close();
DIStream.close();
socket.close();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
response = "{\"Error_no\":5000}";
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
response = "{\"Error_no\":5000}";
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
response = "{\"Error_no\":5000}";
} finally {
if (socket != null) {
try {
socket.close();
if(response == null){
response = "{\"Error_no\":5000}";
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
response = "{\"Error_no\":5000}";
}
}
}
// Log.i("resp",response);
return response;
}
The PHP code:
<?php
echo "service php started \n";
$version = '2.2.0';
$address = '10.164.2.1';
$port = 4444;
$timeout= 2;
$cmd = explode("*", str_replace(array("/"), "*",
str_replace(" ","",shell_exec("netstat -tulpn | grep :".$port))));
echo "pid ".$cmd[1];
$cmd[1] = substr_replace($cmd[1], '', 0, 6);
echo "pid ".$cmd[1];
exec("kill -9 $cmd[1]");
sleep(1);
$socketPath = 'unix:///home/root/sockets/local_iapp_socket';
// Create WebSocket.
$server = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_option($server, SOL_SOCKET, SO_REUSEADDR, 1);
if(socket_bind($server, $address, $port)){
echo "Connected with tcp socket \n";
}else{
echo "connection with tc socket error \n";
}
socket_listen($server);
echo "server is listning \n";
$socket_fd = connect_socket_local();
echo "connected to unix socket \n";
while ($client = socket_accept($server)) {
$num_cmd = socket_read($client, 5000);
echo "Client Message : ".$num_cmd ."\n";
if($socket_fd != false){
$id=24;
$len= strlen($num_cmd);
$fwrite1 = fwrite($socket_fd, pack("L", $len),4);
if($fwrite1 === false){
$content = '{"Error_no":5000}';
echo "fwrite1 a échoué : raison : " . socket_strerror(socket_last_error()) . "\n";
exit;
}
$fwrite2 = fwrite($socket_fd,pack("L", $id),4);
if($fwrite2 === false){
$content = '{"Error_no":5000}';
echo "fwrite2 a échoué : raison : " . socket_strerror(socket_last_error()) . "\n";
exit;
}
$fwrite3 = fwrite($socket_fd,$num_cmd,strlen($num_cmd));
if($fwrite3 === false){
$content = '{"Error_no":5000}';
echo "fwrite3 a échoué : raison : " . socket_strerror(socket_last_error()) . "\n";
exit;
}
$content = fread($socket_fd, 5000) ;
if( $content == null){
echo "impossible d'atteindre la socket locale" . socket_strerror(socket_last_error()) . "\n";
$content = '{"Error_no":5000}';
}
}else{
$content = '{"Error_no":5000}';
echo "problème de connexion" . socket_strerror(socket_last_error()) . "\n";
}
$json_resp = $content;
echo "json_resp" . $json_resp."\n\r";
socket_write($client, $json_resp,strlen($json_resp));
socket_close($client);
}
socket_close($server);
function connect_socket_local()
{
global $socketPath , $timeout;
if (($socket_fd= stream_socket_client($socketPath , $errorno, $errorstr, $timeout)) === false) {
echo "stream_socket_client a échoué : raison : " . socket_strerror(socket_last_error()) . "\n";
}
return $socket_fd;
}
?>

Answer 1

You can run a separate server process for each client. Each server process needs to have an unique IP address or TCP port. Each client needs to be configured to connect to the correct server address and port. This is difficult to manage and doesn't scale.
At the server side, you can get the peer address, that is the IP address and port of the client. In PHP, you can use socket_getpeername() for this. However, depending on the network setup, this might not be the IP address of the client itself. It can be the IP address of an intermediate gateway or other network device. Also, the client IP address might be dynamic.
The best solution is to send some identification from the client to the server when the clients connects to the server. This can be a name or some other unique identification. You have to change the protocol between the client and server to support this. The client needs to know when and how to send the identification. The server needs to know when and how to receive the identification.