How to use WebSocket and JavaScript to achieve online whiteboard collaboration

How to use WebSocket and JavaScript to achieve online whiteboard collaboration

Part 1: Overview

Online whiteboard collaboration refers to multiple users connecting through the network in real time Carry out drawing, annotation and other operations on the same whiteboard, and be able to see the operations of other users. In this article, we will introduce how to use WebSocket and JavaScript to implement online whiteboard collaboration.

Part 2: Introduction to WebSocket

WebSocket is a network protocol for two-way communication between the client and the server. Compared with the traditional HTTP protocol, WebSocket has lower latency and higher real-time performance, which is very suitable for realizing real-time collaboration functions.

Part 3: Establishing a WebSocket connection

In JavaScript, we can use the WebSocket API to establish a WebSocket connection with the server. The following is a simple example:

let socket = new WebSocket("ws://example.com/socket");

In this example, we use new WebSocket to create a WebSocket object and pass in the server address. The address here starts with ws://, which means the WebSocket protocol is used.

Part 4: Handling WebSocket Events

The WebSocket object has some events, and we can handle these events by registering event listeners. The following are examples of some commonly used events and their processing methods:

// 建立连接
socket.onopen = function(event) {
  console.log("WebSocket连接已建立");
};

// 收到消息
socket.onmessage = function(event) {
  let message = event.data; // 接收到的消息数据
  console.log("收到消息：" + message);
};

// 连接关闭
socket.onclose = function(event) {
  console.log("WebSocket连接已关闭");
};

// 发生错误
socket.onerror = function(event) {
  console.error("WebSocket错误");
};

In these event processing functions, we can handle different events accordingly. For example, in the event processing function that receives the message, we can parse the received message and process it.

Part 5: Implement whiteboard collaboration

When implementing the whiteboard collaboration function, we can define some protocols and message formats. For example, we can agree to use messages in JSON format and encapsulate drawing and annotation instructions into corresponding messages.

The following is a simple whiteboard collaboration example:

// 接收到消息时的处理函数
socket.onmessage = function(event) {
  let message = JSON.parse(event.data);
  
  // 根据消息类型进行处理
  switch(message.type) {
    case "draw":
      drawOnWhiteboard(message.data); // 绘画指令
      break;
    case "annotate":
      annotateOnWhiteboard(message.data); // 标注指令
      break;
    // 其他类型的消息处理...
  }
};

// 发送绘画指令
function sendDrawCommand(data) {
  let message = {
    type: "draw",
    data: data
  };
  
  socket.send(JSON.stringify(message));
}

// 发送标注指令
function sendAnnotateCommand(data) {
  let message = {
    type: "annotate",
    data: data
  };
  
  socket.send(JSON.stringify(message));
}

In this example, we define the drawOnWhiteboard and annotateOnWhiteboard functions to handle drawing and Mark the command and send the message of the corresponding command through the sendDrawCommand and sendAnnotateCommand functions.

Part 6: Summary

By using WebSocket and JavaScript, we can realize the function of online whiteboard collaboration. WebSocket provides two-way communication capabilities, and JavaScript can easily handle WebSocket events and send messages. By properly designing protocols and message formats, we can implement whiteboard applications for real-time collaboration. I hope this article will help you understand how to use WebSocket and JavaScript to achieve online whiteboard collaboration.

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