Multiple connections with PHP Socket to receive HTTP messages and save to Mysql

Question

I need to set up a port on my dedicated server that runs the Centos 6.10 kvm OS, so that it receives messages (geolocation) from some trackers via TCP (IP:PORT), and saves this data in the Mysql database by connecting a PHP script.

What has already been done:

1) I opened the TCP port 49100 using the terminal with the following commands:

> iptables -I INPUT -p tcp --dport 49100 -j ACCEPT
> iptables -nL |grep 49100
# ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:49100

2) I used a PHP script to connect to the port and accept multiple connections.

php server.

#!/usr/local/bin/php -q
<?php
error_reporting(E_ALL);

/* Allow the script to hang around waiting for connections. */
set_time_limit(0);

/* Turn on implicit output flushing so we see what we're getting
 * as it comes in. */
ob_implicit_flush();

$address = getHostByName(getHostName()); //IP LOCAL;
$port = 49100;

if (($sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) === false) {
    echo "socket_create() failed: reason: " . socket_strerror(socket_last_error()) . "<br>";
}

if (socket_bind($sock, $address, $port) === false) {
    echo "socket_bind() failed: reason: " . socket_strerror(socket_last_error($sock)) . "<br>";
}

if (socket_listen($sock, 5) === false) {
    echo "socket_listen() failed: reason: " . socket_strerror(socket_last_error($sock)) . "<br>";
}

do {
    if (($msgsock = socket_accept($sock)) === false) {
        echo "socket_accept() failed: reason: " . socket_strerror(socket_last_error($sock)) . "<br>";
        break;
    }
    /* Send instructions. */
    $msg = "<br>Welcome to the PHP Test Server. <br>" .
        "To quit, type 'quit'. To shut down the server type 'shutdown'.<br>";
    socket_write($msgsock, $msg, strlen($msg));

    do {
        if (false === ($buf = socket_read($msgsock, 2048, PHP_NORMAL_READ))) {
            echo "socket_read() failed: reason: " . socket_strerror(socket_last_error($msgsock)) . "<br>";
            break 2;
        }
        if (!$buf = trim($buf)) {
            continue;
        }
        if ($buf == 'quit') {
            break;
        }
        if ($buf == 'shutdown') {
            socket_close($msgsock);
            break 2;
        }
        $talkback = "PHP: You said '$buf'.<br>";
        socket_write($msgsock, $talkback, strlen($talkback));
        echo "$buf<br>";
    } while (true);
    socket_close($msgsock);
} while (true);

socket_close($sock);
?>

client.php

<?php
error_reporting(E_ALL);
$host = getHostByName(getHostName()); //IP LOCAL;
$port = 49100;
// No Timeout 
set_time_limit(0);

/* Turn on implicit output flushing so we see what we're getting
 * as it comes in. */
ob_implicit_flush();

$message = 'Olá, mundo!';

//Create Socket
$socket = socket_create(AF_INET, SOCK_STREAM, 0) or die("Could not create socket\n");

//Connect to the server
$result = socket_connect($socket, $host, $port) or die("Could not connect toserver\n");

//Write to server socket
socket_write($socket, $message, strlen($message)) or die("Could not send data to server\n");

//Read the response from the server
$result = socket_read ($socket, 1024) or die("Could not read server response\n");
echo "Reply From Server  :" . $result;

//Close socket
socket_close($socket);
?>

I opened the browser and opened server.php and client.php, in that order.

client.php returned:

Reply From Server : Welcome to the PHP Test Server. To quit, type 'quit'. To Shut down the server type 'shutdown'.

server.php returned:

Warning: socket_read(): Unable to read from socket [104]: Connection reset by peer in /home/usuario/public_html/server.php on line 37 socket_read() failed: Reset connection by peer

---

The process of opening door 49100 was apparently successful. I have the following questions:

1) What is causing this Warning on the server.php?

2) How can I associate port 49100 to the PHP script so that every connection made by this port runs the script and receives the data sent?

Answer 1

The problem is that as soon as the client receives the welcome message from the server he is running the socket_close function and terminating the connection.

This way, when the server tries to send a second message to the client the connection has already been terminated.

What you should do is use a while on your client so that it waits for the server to reply, instead of closing the connection.

That is, both client and server need to be in a while to be able to send several messages to each other... only after the last message is that the client must terminate the while and close the connection.