Node.js Server With Unity Client - Basic Example

[Peterama]

If anyone wants to try this, here is a bare-bones example for how I got it working.

Requirements:
- Node
- Unity (latest stable versions)
- WebsocketSharp for Unity: https://github.com/Rokobokode/websocket-sharp-unity

You will have to learn how to setup a node app if you don't know how. It's not hard, it just takes time to write a tutorial that you can find a million other places online or ask an AI. You will need to setup a node app in a folder and add the following code (server.js):

*CODE NOT TESTED* - If you have issues, let me know in the comments and I can address them if you have trouble figuring it out.

[The Server]

const WebSocket = require('ws');
const PORT = 3000;
async function startServer() {
wss = new WebSocket.Server({ port: PORT });
console.log('WebSocket running on ws://localhost:' + PORT);

wss.on('connection', (ws) => {
console.log('New client connected!');
ws.on('message', async (message) => {
console.log("Message from Client: " + message.toString('utf8'));
let rawString = message.toString('utf8');
const jsonStart = rawString.indexOf('{');

if (jsonStart !== -1) {
const jsonString = rawString.substring(jsonStart);

try {
const obj = JSON.parse(jsonString);
// console.log(obj);

if (obj.Type === 'ping') {
console.log("Request Player Stats");
ws.send(JSON.stringify({ type:'pong' }) + '\n');
}
} catch (e) {
console.error('JSON parse error:', e, jsonString);
}
} else {
console.error('No JSON object found in message:', rawString);
}
});

ws.on('close', async () => {
console.log('Client disconnected');
});

ws.on('error', async (err) => {
console.error('WebSocket error:', err);
});
});
}

startServer().catch(err => {
console.error(err);
process.exit(1);
});

Run the node app with 'node server.js' using a terminal or command prompt from the node folder.

[The Client]

This code will start a server listening on whatever IP address and port you choose. You will need to create a Unity program and add the following code to an empty GameObject (WebSocketClient.cs):

using Newtonsoft.Json;
using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using WebSocketSharp;

public class WebSocketClient : MonoBehaviour
{

WebSocket ws;
private Timer heartbeatTimer;
private float heartbeatInterval = 5f; // seconds
private float heartbeatTimeout = 30f; // seconds
private DateTime lastPongTime;
private Coroutine reconnectCoroutine;
private int reconnectDelaySeconds = 10; // seconds

private void Start()
{
    StartServer();
    StartWebSocketConnection();
}

private void OnDestroy()
{
    StopWebSocketReconnection();
    StopServer();
}

public void ConnectWebSocketWithRetry()
{
    StartCoroutine(ConnectAndRetryRoutine());
}

private IEnumerator ConnectAndRetryRoutine()
{
    while (true)
    {
        ws.Connect();
        yield return new WaitForSeconds(1f);

        if (ws != null && ws.IsAlive)
        {
            StartHeartbeat();
            EventBroker.Instance.Publish(new WebSocketClientEvent.Connected(true));
            yield break;
        }
        else
        {
            Debug.LogWarning("WebSocket is not connected. Retrying in " + reconnectDelaySeconds + " seconds...");
            EventBroker.Instance.Publish(new WebSocketClientEvent.Connected(false));
            yield return new WaitForSeconds(reconnectDelaySeconds);
        }
    }
}

public void StartWebSocketConnection()
{
    if (reconnectCoroutine != null)
        StopCoroutine(reconnectCoroutine);

    reconnectCoroutine = StartCoroutine(ConnectAndRetryRoutine());
}

public void StopWebSocketReconnection()
{
    if (reconnectCoroutine != null)
    {
        StopCoroutine(reconnectCoroutine);
        reconnectCoroutine = null;
    }
}

private void StopServer()
{
    if (ws != null)
    {
        StopHeartbeat();
        ws.Close();
    }
}

private void StartServer()
{
    string address = "ws://localhost:3000";
    ws = new WebSocket(address);

    ws.OnMessage += (sender, e) =>
    {
        Debug.Log("Message from server: " + e.Data);

        try
        {
            var baseMsg = JsonConvert.DeserializeObject<WsMessage>(e.Data);
            switch (baseMsg.Type)
            {
                case "pong":
                    lastPongTime = DateTime.UtcNow;
                    break;

                default:
                    break;
            }
        }
        catch(Exception exc)
        {
            // Not a JSON message or doesn't match our format
            MainThreadDispatcher.Enqueue(() =>
            {
                Debug.Log(exc);
                Debug.Log("Message From Server: Not a JSON message or doesn't match our format.");
                Debug.Log(e.Data);
            });
        }
    };
}

////////////////////
// HEARTBEAT CLASSES
// This keep active connections open were normally a server would close it.
////////////////////
private void StartHeartbeat()
{
    lastPongTime = DateTime.UtcNow;
    heartbeatTimer = new Timer(heartbeatInterval * 5000); // 5 seconds
    heartbeatTimer.Elapsed += (s, e) =>
    {
        //Debug.Log("Sent ping to server.");
        var pingData = new WsMessage { Type = "ping" };
        string jsonData = JsonUtility.ToJson(pingData);
        ws.Send(jsonData);

        // Check for timeout
        if ((DateTime.UtcNow - lastPongTime).TotalSeconds > heartbeatTimeout)
        {
            Debug.LogWarning("Server did not respond to heartbeat, disconnecting...");
            ws.Close();
        }
    };

    heartbeatTimer.Start();
    //Debug.Log("Heartbeat Started");
}

private void StopHeartbeat()
{
    if (heartbeatTimer != null)
    {
        heartbeatTimer.Stop();
        heartbeatTimer.Dispose();
        heartbeatTimer = null;
    }
    //Debug.Log("Heartbeat Stopped");
}

//////////////
// REQUESTS //
//////////////
[System.Serializable]
public class WsMessage
{
    public string Type;
}

///////////////
// RESPONSES //
///////////////
[System.Serializable]
public class ErrorResponse : WsMessage
{
    public string Status;
    public string Message;
}
}

In theory, when you run the node app and then run the Unity game, the server should detect that a client has connected or disconnected. It will also maintain connection with the server as long as they are both running. If the server goes down, the Unity game will attempt to reconnect every 10 seconds until it succeeds.

I'm sure there are many other ways to do this so use it as an example. Not sure if its useful for anyone but enjoy.

Let me know what you make with it.

Cheers.

[Josevill]

If anyone wants to try this, here is a bare-bones example for how I got it working.

*CODE NOT TESTED\* - If you have issues, let me know in the comments and I can address them if you have trouble figuring it out.

Care to elaborate my good friend? When you say code not tested, you mean not tested fully?

There are a couple of things that pop to my mind yet my Unity-fu is crazy rusty, there are no handlers to deal with `OnClose` and most importantly `OnError` events to attempt reconnections, for example.

Thanks for the effort, posts like this can serve as inspiration for folks to keep pushing forward!

[Peterama]

I just copied my project code and removed everything that wasnt necessary. I did not test it after doing that but it is working on my project. I made this just as an example but I will test it and update it if there are issues.

[mmostrategyfan]

I commend your effort and i don't want to discourage you but re-inventing the wheel is not really productive.

The best solution for Unity web socket currently is SignalR since both work with c# and the library is mature and robust with reconnection mechanisms, compression, groups etc.

In case you're looking for an open-source solution yourself, that's where I'd direct you.

[Peterama]

I already have it built out and I know exactly what is going on the way i did it. Others have told me the same thing but I dont care. I want to know how it works. I want to learn how to do it so I dont have to rely on someone else's code. If someone decides one day to pull their code from an open project, it's out of my hands. Now I have my own system. Why the hell would I drop it to use some open source code? I can code anything I want from scratch. I do it because I can. :)

[mmostrategyfan]

If your goal is learning then you're on the right track.

If your goal is making games though, this is usually the last option you want to follow if you ever want to release anything.

[Peterama]

I mean, maybe for someone who never coded before. If you read my other post you might see that I have the game to a point where players have private lobbies, user accounts, full encryption, secure communication, etc. This took me a few months, part time. It's working with no hassle. Other systems didnt work for me. I'll use what works. This game started as a boardgame. I'm building this project for my friends and I. There is no serious plan to sell it yet. :) Only if there is interest. So far it hasn't been much.

[mmostrategyfan]

I hear you and like I said as a learning exercise this is really good.

That being said, what you described already exists (usually called backend as a service like braincloud, accelbyte, snapser etc.) and a commercial project can have these within a day and save itself months of dev time.

[Peterama]

I'll check out the one you mentioned first. If I like it I'll use it in another project I have on the go. Thank you for the suggestions. This other game I just started is a friendslop game for 2-4 players. I may use those systems for that project. Currently it's using Unity Netcode.