How Swoole supports WebSocket's disconnection and reconnection function

WebSocket has become a common protocol in modern Web development. It can establish a two-way communication channel between the client (browser) and the server. However, unstable network environment or other unknown reasons may cause unexpected disconnection of WebSocket, which will cause great trouble to developers in development and maintenance.

Swoole is a high-performance network communication framework for PHP. It supports the WebSocket protocol and provides the WebSocket disconnection and reconnection function. This article will introduce how Swoole implements the disconnection and reconnection function of WebSocket, hoping to help developers better cope with unstable network environments.

WebSocket disconnection and reconnection scenarios

The demand for the WebSocket disconnection and reconnection function mainly occurs in the following scenarios:

1. The network environment is unstable.
2. The client closed the browser or other reasons caused the client to disconnect.
3. An exception occurred on the server side, causing the connection to be interrupted.

In these cases, if there is no disconnection and reconnection function, it will cause the user to log in again, reconnect and other operations, which will have a great impact on the user experience.

WebSocket disconnection and reconnection function provided by Swoole

Swoole's support for the WebSocket protocol is very comprehensive and complete. It provides a series of event callback functions that allow us to implement these functions. WebSocket's disconnection and reconnection function.

The following are some callback functions provided by Swoole:

• onOpen: The callback function when the WebSocket connection is opened.
• onMessage: Callback function when receiving a WebSocket message.
• onClose: Callback function when the WebSocket connection is closed.

Among them, the onClose function is the key function to realize WebSocket disconnection and reconnection.

When the connection between the client and the server is closed, we can implement the disconnection and reconnection logic in the onClose event callback function. The specific implementation plan is as follows:

1. Record the unique identifier of the connection (such as user name, device number, etc.).
2. Determine whether the connection is closed due to network problems, client shutdown, or server exception.
3. If the shutdown is caused by a network problem, we can try to reconnect within a certain period of time (usually a few seconds).
4. If we still cannot connect, we can take some actions, such as prompting the user, recording logs, etc.

Code implementation of WebSocket disconnection and reconnection

The following is a sample code that shows how to use Swoole to implement the disconnection and reconnection function of WebSocket:

on('open', function ($server, $request) {
    echo "Client {$request->fd} connected
";
});

//接收到消息时
$server->on('message', function ($server, $frame) use (&$connections) {
    echo "Received message: {$frame->data}
";
});

//连接关闭时
$server->on('close', function ($server, $fd) use (&$connections) {
    echo "Connection {$fd} closed
";
    
    // 遍历所有连接，找到断开的连接的标识符，并删除记录
    foreach($connections as $key => $value){
        if($value == $fd){
            unset($connections[$key]);
        } 
    }
    
    // 重连
    swoole_timer_after(5000, function() use ($fd, &$connections){
        if (!in_array($fd, $connections)) {
            $connection = new swoole_http_client('127.0.0.1', 9501);
            $connection->upgrade('/', function ($client) use ($fd, &$connections){
                echo "Connection {$fd} reconnected
";
                $connections[$client->sock] = $fd;
            });
        }
    });
});

$server->start();

In the above code, when the connection is closed, we use the swoole_timer_after function to implement the disconnection and reconnection function. This function indicates that a callback function will be executed after a certain time interval.

The specific operations are as follows:

1. Determine whether the current connection is recorded in the $connections array.
2. If it is not recorded, it means you need to reconnect. Create a swoole_http_client object and set the corresponding IP and port.
3. Call the upgrade method to realize the connection of WebSocket protocol. When the connection is successfully established, we record the correspondence between the file descriptor and identifier of the connection.

Through this implementation, we can realize the disconnection and reconnection function of WebSocket when the network environment is unstable.

Summary

In modern Web development, WebSocket has become an important protocol. However, unstable network environment or other unknown reasons may cause the WebSocket connection to be abnormally disconnected, which will cause trouble to developers.

Swoole is a high-performance network communication framework that supports the WebSocket protocol and provides a series of event callback functions that allow us to implement the WebSocket disconnection and reconnection function. Through the introduction of this article, I hope it can help developers better understand and apply Swoole.

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