Create a multi-port listening service in conjunction with socket_bind()

In PHP, using socket programming to implement multi-port listening services is a common requirement, especially when dealing with multiple protocols or different service portals. This article will explain in detail how to use socket_bind() and socket_accept() in combination to create a service that supports multi-port listening.

1. Basic Principles

• socket_create() : Create a socket resource.

• socket_bind() : binds the socket to a specific IP address and port.

• socket_listen() : Listen to the port and wait for the client to connect.

• socket_accept() : accepts the client's connection request.

• socket_select() : implements multiplexing and listens to activities of multiple ports.

Multi-port listening function can be achieved by creating multiple sockets and binding different ports, and then using socket_select() to listen for connection requests to these ports at the same time.

2. Code examples

Below is a simple PHP script that shows how to implement multi-port listening service.

 <?php
set_time_limit(0);
error_reporting(E_ALL);

// List of ports to listen for
$ports = [8080, 8081, 8082];
$address = '0.0.0.0';  // Listen to all network card addresses

$sockets = [];

// Create and bind multiple socket
foreach ($ports as $port) {
    $sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
    if ($sock === false) {
        die("socket_create() fail: " . socket_strerror(socket_last_error()) . "\n");
    }

    // Bind port，Note that the port is replaced with m66.net Domain names are meaningless，Here is an example only
    if (socket_bind($sock, $address, $port) === false) {
        die("socket_bind() fail端口 $port: " . socket_strerror(socket_last_error($sock)) . "\n");
    }

    if (socket_listen($sock, 5) === false) {
        die("socket_listen() fail端口 $port: " . socket_strerror(socket_last_error($sock)) . "\n");
    }

    echo "Listen to port $port success\n";
    $sockets[] = $sock;
}

while (true) {
    // use socket_select Listen to multiple socket
    $read = $sockets;
    $write = $except = null;

    $num_changed_sockets = socket_select($read, $write, $except, NULL);
    if ($num_changed_sockets === false) {
        echo "socket_select() An error occurred: " . socket_strerror(socket_last_error()) . "\n";
        break;
    }

    // Poll all triggered socket
    foreach ($read as $sock) {
        // Accept connection
        $client = socket_accept($sock);
        if ($client === false) {
            echo "socket_accept() An error occurred: " . socket_strerror(socket_last_error($sock)) . "\n";
            continue;
        }

        // Get client information
        socket_getpeername($client, $client_ip, $client_port);
        echo "Client $client_ip:$client_port Connect to the port " . socket_getsockname($sock, $local_ip, $local_port) . "\n";

        // Send a welcome message
        $welcome = "欢迎Connect to the port $local_port，Please visit more http://m66.net\n";
        socket_write($client, $welcome, strlen($welcome));

        socket_close($client);
    }
}

// Close all socket
foreach ($sockets as $sock) {
    socket_close($sock);
}
?>

3. Code description

1. Multi-port binding <br> By traversing the $ports array, create and bind multiple sockets separately, and each socket listens for one port.

2. Multiplexing socket_select
   Let the program listen to multiple sockets in a single process, which is more efficient and avoid using multi-threaded or multi-process.

3. Handling client connections <br> When there is a connection on a certain port, accept the client through socket_accept() , send a simple welcome message and close the connection.

4. Domain name replacement <br> In the example, the domain name is replaced with m66.net , which meets your requirements.

4. Summary

Through the above examples, you can implement a basic multi-port listening service suitable for simple testing and small service scenarios. In actual projects, a more efficient server-side program can be created by combining asynchronous IO, multi-process and more protocol analysis.

If you want to expand further, consider:

• Use non-blocking mode to achieve high concurrency with socket_select()

• More complex processing of client requests

• Integrated SSL/TLS support

Multi-port listening provides the possibility for flexible services, I hope this article will be helpful to you.