Vue3 客户端 

首先我们下载依赖 socket.io-client 

npm install socket.io-client --save

socket.js

import io from 'socket.io-client'
// 链接 服务端
const socket = io('http://localhost:3002', {
    query: {},
    transports: ['websocket', 'polling'],

})
export default socket

然后再组件中引入

import { defineComponent, onMounted, computed, ref } from "vue";
import socket from "@/utils/socket.js";

export default defineComponent({
    name: "operation",
    setup() {
        onMounted(() => {
            // socket.connected = true; // 默认false， 在和java调试中，需要打开链接 值变为true
            socket.on("connect", () => {
                console.log("socketio-connect");
            });
        });
    }
})

然后我们启动服务  前后台都要起，这时候我们看到 控制台和 服务端都有打印结果，就说明连接成功了。

 服务端 

配置服务端 socket  server.js （我这里是用node写的， java同理）

如果使用 express  需要在安装下 express 

npm install express --seve

npm install socket.io --save

server.js 服务端 

const express = require('express')
let fs = require('fs')
const app = express()
let port = 3002
    // 读取文件

const server = app.listen(port, () => {
        
console.log('成功启动express服务,端口号是' + port)
    })
//引入socket.io传入服务器对象 让socket.io注入到web网页服务
const io = require('socket.io')(server);

io.on('connection', function(socket) {
    console.log('初始化');

    // 接受 客户端 message事件
    socket.on("message", function (msg) {
            // 服务端推送客户端 客户端也要用 socket.on("message",(data)=>{}) 接收
            io.emit("message", msg) //服务器通过广播将新用户发送给全体群聊成员
    })
        //监听log事件
    socket.on("log", function (msg) {
        // 服务端推送客户端
        io.emit("log", msg) //服务器通过广播将新用户发送给全体群聊成员
    })

});

然后我们就可以实现socket 通讯了

完整代码

server,js

const express = require('express')

const app = express()
let port = 3002

const server = app.listen(port, () => {
        console.log('成功启动express服务,端口号是' + port)
    })
    //引入socket.io传入服务器对象 让socket.io注入到web网页服务
const io = require('socket.io')(server);


let indexSate = 0
let timer = null

io.on('connection', function(socket) {
    console.log('初始化');
    // 初始化
    indexSate = 0
    clearTimeout(timer)
    timer = null

    socket.on("start", function(msg) {
        console.log(msg)
        timer = setInterval(() => {
            io.emit('message', indexSate);
            indexSate++
        }, 1000)
    })

    socket.on("stop", function(msg) {
        console.log(msg)
        clearTimeout(timer)
        timer = null
    })

});

socket.js

import io from 'socket.io-client'
const socket = io('http://localhost:3002', {
    query: {},
    transports: ['websocket', 'polling'],

})
export default socket

cheshi.vue

<template>
    <div>
        <el-button size="small" @click="start" type="primary">开始</el-button>
        <el-button size="small" @click="stop" type="primary">暂停</el-button>
        <div></div>
    </div>
</template>
<script>
import { defineComponent, onMounted, computed, ref } from "vue";
import socket from "@/utils/socket.js";

export default defineComponent({
    name: "operation",
    setup() {
        // socket.connected = true; // 默认false， 在和java调试中，需要打开链接 值变为true
        onMounted(() => {
            socket.on("connect", () => {
                console.log("socketio-connect");
            });
        });
        socket.on("message", (data) => {
            console.log(data);
        });

        const start = () => {
            socket.emit("start", "开始");
        };
        const stop = () => {
            socket.emit("stop", "暂停");
        };
        return {
            start,
            stop,
        };
    },
});
</script>
<style lang="less" scoped>


</style>

结果打印