How to use Swoole to implement TCP relay server

Swoole is a high-performance network communication framework based on PHP language. It provides asynchronous, concurrency, event-driven and other features, and supports TCP, UDP, HTTP, WebSocket and other protocols. In this article, we will explore how to use Swoole to implement a TCP relay server, while providing specific code examples.

TCP relay server is generally used to transfer data on the network. For example, a client A wants to send data to another client B, but A and B cannot communicate directly. In this case, they can use TCP relay server to forward data.

To implement the TCP relay server, you need to pay attention to the following points:

1. Receive the client’s connection request and create the corresponding connection
2. Listen to all connected data and transfer the data Forward to the target connection
3. Handle the connection disconnection and clean up the connection resources in time

The following uses a specific example to demonstrate how to use Swoole to implement a TCP relay server.

First, we define an array to store the information of each client connection:

$clients = [];

Then, create a Swoole TCP server object and set the relevant parameters:

$server = new swoole_server("0.0.0.0", 9501);

$server->set([
    'worker_num' => 1,         //worker进程数
    'max_request' => 1000,     //每个worker最多处理1000个请求
    'dispatch_mode' => 2,      //使用固定模式
    'debug_mode' => 1,         //调试模式
]);

When the server starts, we register a callback function to handle connection events:

$server->on('connect', function ($server, $fd) {
    echo "Client: Connect.
";
    //将连接信息存入数组
    $clients[$fd] = [
        'id' => $fd,
        'remote_ip' => $server->getClientInfo($fd)['remote_ip'],
        'remote_port' => $server->getClientInfo($fd)['remote_port'],
        'target_fd' => 0  //默认为0
    ];
});

When a client connects to the server, the message "Client: Connect." will be output and the The client connection information is stored in an array.

Next, we register a callback function to process the received data:

$server->on('receive', function ($server, $fd, $from_id, $data) use (&$clients) {
    //如果还没有目标连接，则需要先选择一个
    if (empty($clients[$fd]['target_fd'])) {
        foreach ($clients as $client) {
            if ($client['id'] != $fd && empty($client['target_fd'])) {
                $clients[$fd]['target_fd'] = $client['id'];
                $clients[$client['id']]['target_fd'] = $fd;
                break;
            }
        }
    }

    //将数据转发到目标连接
    $server->send($clients[$fd]['target_fd'], $data);
});

When there is data transmission, the data content will be obtained. According to the client connection information, an unused data will be found. Use the target connection to forward the data through the target connection.

Finally, we register a callback function to handle the connection disconnection event:

$server->on('close', function ($server, $fd) use (&$clients) {
    echo "Client: Close.
";
    //清理连接信息
    if (!empty($clients[$fd]['target_fd'])) {
        $target_fd = $clients[$fd]['target_fd'];
        $clients[$target_fd]['target_fd'] = 0;
    }
    unset($clients[$fd]);
});

When a client connection is disconnected, the message "Client: Close." will be output, and Clean up connection information.

The above is the implementation of a simple TCP relay server. Through the above code example, we can see that using Swoole to implement a TCP relay server is very simple. You only need to define relevant parameters, register a callback function, and target Just write the corresponding logic for each event.

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