Make a multiplayer card game - Episode 4 | Play cards with other players

This section is a milestone in this series of tutorials, and after this article, there will present a complete multiplayer local online card game.

The key point of this section is how to link multiplayer to play.

Almost all changes is on the server side:

We make a server and listen on "connection" event.

const net = require('net');
const server = net.createServer();

Then we generate a player ID and seat number for the player connecting.

var playerIDArr = [];
function generatePlayerIDAndSeatNumber() {
    let _seat = playerIDArr.length;
    let _id = Math.floor(Math.random() * 10000);
    let _isExist = playerIDArr.indexOf(_id) != -1;
    if (_isExist) {
    } else {
    return { id: _id, seat: _seat };

Back to the "connection" event, we assign some attributes on socket to make a identification.

server.on("connection", (socket) => {
    let _id_seat = generatePlayerIDAndSeatNumber();
    let _playerID =;
    let _seatNumber =; = _playerID; = _seatNumber;
    socketDic[_playerID] = socket;


Add event listener to each socket, listen players' interaction information through data which cotain the command ID to route different game logic:

function addSocketListener(socket) {
    socket.on('data', (data) => {
        let _playerID =;
        decodeData(data, _playerID);
    socket.on('error', (error) => {
        //player disconnect

the server forwards each player's messages, which are divided into separate sending and broadcasting.

//send to a specific player
function send(playerID, cmd, data) {
    if (!mIsGaming) return;
    const _dataBuffer = encodeData(cmd, data);
    if (_dataBuffer) socketDic[playerID].write(_dataBuffer);
//send to all players
function broadcast(cmd, data) {
    if (!mIsGaming) return;
    const _dataBuffer = encodeData(cmd, data);
    if (_dataBuffer) {
        let _keyArr = Object.keys(socketDic);
        for (let i = 0; i < _keyArr.length; i++) {
            let _socket = socketDic[_keyArr[i]];

That's all the key points in this section, as above present, players can be connect to a server and play with each other. You can check episode4 tag to see the complete code.

The progress of the project up to this point have make a milestone, will not add new content to the relevant repo main branch, excluding the subsequent refactoring to prepare for the involvement of the game engine and framework.

The addition of new content will open another branch for development. Like each episode, a tag will still be added after the chapter ends. You can find the content of the corresponding chapter through the corresponding tag at any time.

In order to reflect the simplicity of native nodejs, I chose javascript. But I have been developing with typescript in the past few years, is not very familiar with javascript, which I must spend a little bit more time on debugging.

The content of the following chapters will expand rapidly. For either the robustness of development or my proficiency. I will use typescript for new content development and refactoring in later articles.

The next episode, as the content list in the first episode, I will add game engine Cocos Creator, before which I will make a refactory, besides move javascript to typescript, but something about modularity.

Thanks for your reading, and discussion is always welcome, I am very glad to talk with you in below comment section😊.

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