How to use golang's Websocket to develop online whiteboard function
Introduction:
In today's Internet era, there are more and more online collaboration tools was developed. Among them, the online whiteboard is a very practical tool that allows users to draw and write on the same page in real time. This article will introduce how to use golang's Websocket to develop a simple online whiteboard function and give specific code examples.
Introduction to Websocket:
Websocket is a protocol for full-duplex communication over a single TCP connection. Different from the traditional HTTP request-response model, Websocket allows the server to actively push data to the client to achieve real-time two-way communication. When we developed the online whiteboard function, Websocket just met our needs.
Development environment:
Before you start, please make sure that golang and related libraries have been installed in your development environment. This article will use github.com/gorilla/websocket as the Websocket library.
Implementation steps:
- Install dependent libraries
Open a terminal or command prompt and execute the following command to install the Websocket library:
go get github.com/gorilla/websocket
- Initialize the project
First, create an empty folder as the root directory of the project. Then, create a file named main.go in that directory. This file will contain our main code.
In the main.go file, import the required libraries and packages:
package main
import (
"log"
"net/http"
"github.com/gorilla/websocket"
)- Create Websocket Processor
In order to handle Websocket connections, we A processor needs to be implemented. Add the following code to the main.go file:
var upgrader = websocket.Upgrader{
CheckOrigin: func(r *http.Request) bool {
return true
},
}
func websocketHandler(w http.ResponseWriter, r *http.Request) {
conn, err := upgrader.Upgrade(w, r, nil)
if err != nil {
log.Println(err)
return
}
defer conn.Close()
// 在此处编写逻辑来处理前端发送过来的事件和数据
}In this code, we create a global websocket.Upgrader object to upgrade the HTTP connection to a Websocket connection. In the websocketHandler function, we use the upgrader object to upgrade the connection and handle subsequent data exchange logic.
- Start the Websocket server
In the main function, we need to register the websocketHandler function we created as an http processing function and listen to the specified port. Add the following code to the main.go file:
func main() {
http.HandleFunc("/ws", websocketHandler)
err := http.ListenAndServe(":8000", nil)
if err != nil {
log.Fatal("Websocket server error:", err)
}
}In this code, we register the websocketHandler function as the Websocket processor with the processing path /ws. Then, we use the http.ListenAndServe function to listen to port 8000 and start the Websocket server.
- Front-end page
In this simple example, we will use HTML and JavaScript to implement the front-end page. In the root directory of the project, create a file called index.html and add the following code:
<!DOCTYPE html>
<html>
<head>
<title>在线白板</title>
<style>
#canvas {
border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="canvas" width="800" height="600"></canvas>
<script>
var ws = new WebSocket("ws://localhost:8000/ws");
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
ws.onopen = function() {
console.log('Websocket连接已建立');
};
ws.onmessage = function(e) {
var data = JSON.parse(e.data);
// 处理从服务器端发送过来的数据
};
ws.onclose = function() {
console.log('Websocket连接已关闭');
};
// 在此处添加绘图逻辑
</script>
</body>
</html>In this code, we create a Canvas element for drawing. We then use the WebSocket object to establish a connection with the server and add handling for the open, message, and close events. In these event handlers, we can write logic to process the data sent from the server.
Finally, run the go run main.go command in the root directory of the project, and then open the index.html file in the browser to experience the online whiteboard function we developed.
Summary:
This article introduces how to use golang's Websocket library to develop a simple online whiteboard function, and gives specific code examples. By reading this article, you can learn how to handle Websocket connections, how to receive and process data from the server, and how to draw images in front-end pages. I hope this article will be helpful to your learning and development!
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