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Together with socket_listen() to create a basic network server

M66 2025-05-28

In PHP, using Socket extensions, we can implement network communication functions very flexibly, and even use it to create a basic network server. This article will focus on how to use socket_listen() and socket_accept() functions to build a simple TCP server.

What are socket_listen() and socket_accept()?

  • socket_listen()
    This function is used to listen for a socket resource with an IP and port bound to wait for the client connection request.

  • socket_accept()
    This function is used to accept an incoming client connection request and returns a new socket resource for communicating with the client.

Basic process analysis

  1. Create socket resource ( socket_create )

  2. Bind IP and port ( socket_bind )

  3. Listen port ( socket_listen )

  4. Looping and accepting client connections ( socket_accept )

  5. Read and write data and complete communication

  6. Close client and server sockets

Sample code

 <?php
// createTCP socket（AF_INETProtocol family，Streaming）
$server = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($server === false) {
    die("socket_create() fail: " . socket_strerror(socket_last_error()) . "\n");
}

// BindIPand ports
$address = '0.0.0.0';  // Listen to all network interfaces
$port = 8080;
if (!socket_bind($server, $address, $port)) {
    die("socket_bind() fail: " . socket_strerror(socket_last_error($server)) . "\n");
}

// Start monitoring，The queue length that allows waiting for connection is5
if (!socket_listen($server, 5)) {
    die("socket_listen() fail: " . socket_strerror(socket_last_error($server)) . "\n");
}

echo "The server is started，monitor {$address}:{$port}\n";

while (true) {
    // Blocking and waiting for client connection
    $client = socket_accept($server);
    if ($client === false) {
        echo "socket_accept() fail: " . socket_strerror(socket_last_error($server)) . "\n";
        continue;
    }

    // Read data from the client，Maximum read1024byte
    $input = socket_read($client, 1024);
    if ($input === false) {
        echo "socket_read() fail: " . socket_strerror(socket_last_error($client)) . "\n";
        socket_close($client);
        continue;
    }

    echo "Received client data: $input\n";

    // Processing data - Here is a simple reply to the client message
    $response = "Hello，Client！The data you send is：" . trim($input) . "\n";
    socket_write($client, $response, strlen($response));

    // 关闭Client连接
    socket_close($client);
}

// Shut down the serversocket（Usually I won&#39;t go here）
socket_close($server);
?>

illustrate

  • In actual use, you can extend the read and write logic according to your needs, such as implementing a complete protocol parser, or processing multiple clients asynchronously.

  • The listener's IP can be set to a specific address, or listen for all available network interfaces using '0.0.0.0' .

  • The port number should be avoided using the system to retain ports, and generally, ports above 1024 should be selected.

  • The above code is a single-threaded server that is synchronously blocked, suitable for beginner understanding.

summary

Through socket_listen() and socket_accept() , PHP can build TCP server programs very directly to realize basic network communication functions. Although PHP is not a language designed specifically for high-performance servers, it is still very practical to use it to quickly prototype small services or make some simple network interaction applications.

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