WebSocket Technical Guide in PHP

With the increasing popularity of web applications, Websocket has become a crucial technology. Websocket technology provides a full-duplex, real-time communication method and continues to evolve within the traditional HTTP request-response model. PHP is a popular scripting language widely used in web development and applications. This article explores the basic concepts, implementation methods and related libraries of WebSocket technology in PHP.

1. What is Websocket technology?

WebSocket technology is a real-time communication protocol based on the TCP protocol. It can establish a two-way communication connection between a web browser and a server to achieve real-time message push and data transmission. It is different from the HTTP request/response model, which requires the client to initiate a request to the server and then wait for the server to respond, which usually requires polling and is inefficient. WebSocket technology allows the server to actively send data to the client without waiting for the client request.

2. Basic concepts of WebSocket

WebSocket uses the same TCP port as the HTTP protocol (default port is 80, 443), and implements handshake through HTTP upgrade protocol. After the handshake is successful, the communicating parties establish a websocket connection and perform data transmission.

The following are the basic concepts in WebSocket:

1. WebSocket connection

WebSocket connection is a two-way communication connection based on the TCP protocol. In Websocket, the cycle of sending data is not determined by the client like HTTP, but is triggered by messages actively sent by the server or client.

2. WebSocket Protocol

The WebSocket protocol is an event-driven protocol that allows data exchange and communication between clients and servers with low overhead and Higher real-time performance.

3. WebSocket Messages

WebSocket messages are similar to HTTP requests, but in WebSocket, messages are sent asynchronously. Compared with HTTP requests, WebSocket messages have the following advantages: smaller bandwidth consumption, less delay, and faster response time.

3. WebSocket implementation method

Below we will introduce how to implement WebSocket technology in PHP.

1. Based on extension library

There are multiple PHP extension libraries available for implementing WebSocket, for example:

PHP-Socket.io: This library implements A WebSocket server that can be used to implement real-time communication.

Ratchet: Ratchet is an implementation of a WebSocket server, based on PHP, React and ReactPHP.

Swoole: Swoole is an asynchronous, high-performance PHP network server that provides a complete WebSocket server implementation.

These libraries are implemented through PHP extension libraries and need to be installed and configured on the server before they can be used.

2. Manual implementation

Manual implementation of WebSocket also requires the implementation of the WebSocket protocol. The WebSocket protocol is based on the HTTP protocol and defines some additional HTTP request header fields.

The following is the handshake process of the WebSocket protocol:

1. The client sends an Upgrade: websocket header to the server; 2. The server returns the Upgrade: websocket header, Connection: Upgrade header, and an SecWebSocketKey header, where the latter is generated based on the client request. 3. The client uses the generated SecWebSocketKey to calculate the SecWebSocketAccept sent by the server to ensure the success of the handshake.
2. After the handshake is successful, data can be sent directly between the server and the client.

Code sample:

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_bind($socket, '127.0.0.1', 8080);
socket_listen($socket);

$clients = [];

while (true) {
    if (($client = socket_accept($socket))) {
        array_push($clients, $client);
    }

    foreach ($clients as $key => $client) {
        $read = socket_read($client, 1024);

        if ($read != null) {
            foreach ($clients as $send_agent) {
                socket_write($send_agent, "client $key : $read");
            }
        }
        else {
            unset($clients[$key]);
        }
    }
}

This is a simple WebSocket server implementation that listens to port 8080, accepts connections from clients, and accepts and sends information.

4. WebSocket application scenarios

The following are some common WebSocket application scenarios:

1. Instant messaging: WebSocket can be used to implement instant messaging and support real-time message sending. and receive.
2. Game client implementation: WebSocket can be used to implement online game clients, providing game players with real-time interactive communication functions.
3. Real-time updates of the stock market: WebSocket can be used for real-time updates of the stock market, making it convenient for users to obtain the latest stock prices and data.
4. Internet of Things communication: WebSocket can be used for communication between IoT devices.

5. Conclusion

WebSocket is a very useful technology. In PHP, we can implement WebSockets in many different ways. Whether you choose to use an extension library or manually implement the WebSocket protocol, using WebSocket can improve the efficiency and real-time performance of Web applications. It is a technology worthy of in-depth study and use by developers.

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