Can't connect to websocket from Unity

[Naokim-NHZ]

Hello,

I'm trying to send data between two unity application, one "main" server on standalone and one "display" on WebGL.
The final goal is to communicate data from a game to a stream overlay.

I'm using the sample code on the main github page for websocket. But I keep receiving the error "WebSocketException: Unable to connect to the remote server" on the client end.
I've check, the port is not used by another program.
The server display the "OnOpen" message but that's it.

Also, I don't understand why on the main page of the git, on the WebSocket sample section, we open the server twice, one time with an "http" address and a second time with a "ws" address. I've try it that way, but it won't work as well. I guess it's copy-paste mistake.

• Here is the full stack :

`WebSocketException: Unable to connect to the remote server
System.Net.WebSockets.WebSocketHandle.ParseAndValidateConnectResponseAsync (System.IO.Stream stream, System.Net.WebSockets.ClientWebSocketOptions options, System.String expectedSecWebSocketAccept, System.Threading.CancellationToken cancellationToken) (at <fba24a13802445559d6435422e829b75>:0)
System.Net.WebSockets.WebSocketHandle.ConnectAsyncCore (System.Uri uri, System.Threading.CancellationToken cancellationToken, System.Net.WebSockets.ClientWebSocketOptions options) (at <fba24a13802445559d6435422e829b75>:0)
System.Net.WebSockets.ClientWebSocket.ConnectAsyncCore (System.Uri uri, System.Threading.CancellationToken cancellationToken) (at <fba24a13802445559d6435422e829b75>:0)
Netly.HTTP+WebsocketTo+<>c__DisplayClass18_0.<Open>b__0 () (at <08183f79570248a0b993e2815da7906c>:0)
UnityEngine.Debug:LogException(Exception)
<>c:<Setup>b__5_1(Exception) (at Assets/Client.cs:34)
Netly.<>c__DisplayClass25_1:<Error>b__1()
Netly.MyMainThread:Dispatch()
Netly.Netly:Update() (at Assets/Plugins/Netly/Netly.cs:14)

• Client code :

public class Client : MonoBehaviour
{
    private HTTP.WebSocket _client;
    
    private const string PATH = "/Hello";
    private const string URI = "ws://localhost:8080";
    
    private Uri _uri;
    
    private void Start()
    {
        Setup();
        Debug.Log($"Try to connect to {_uri}");
        _client.To.Open(_uri);
    }
    
    private void Setup()
    {
        _client = new HTTP.WebSocket();
        _uri = new Uri(URI + PATH);
        
        _client.On.Open(() =>
        {
        Debug.Log("Client opened");
        _client.To.Data("my message", HTTP.Text);
        });
        
        _client.On.Error(exception => Debug.LogException(exception));
        
        _client.On.Close(() => Debug.Log("Client closed"));
    }

    private void OnDestroy() => _client.To.Close();
}

• Server code :

public class Server : MonoBehaviour
{
    private HTTP.Server _server;
    
    private const string PATH = "/Hello";
    private const string URI = "ws://localhost:8080";
    
    private Uri _uri;
    
    [Button]
    private void StartServer()
    {
        Setup();
        _server.To.Open(_uri);
    }
    
    private void Setup()
    {
        _server = new HTTP.Server();
        _uri = new Uri(URI);
    
        SetupRoute();
        
        _server.On.Open(() => Debug.Log($"Server opened at {_uri}"));
        _server.On.Error(exception => Debug.LogException(exception));
        _server.On.Close(() => Debug.Log("Server closed"));
    }
    
    private void SetupRoute()
    {
        _server.Map.WebSocket(PATH, (req, ws) =>
        {
            Debug.Log("is this called ?");

            ws.On.Open(() => Debug.Log($"Open {PATH} connection"));
            
            ws.On.Close(_ => Debug.Log($"Close {PATH} connection"));
            
            ws.On.Error(exception => Debug.LogException(exception));
            
            ws.On.Data((bytes, type) => Debug.Log($"Received {bytes} on {PATH} channel"));
            
            ws.On.Event((name, bytes, type) => Debug.Log($"Received event {name} : {bytes} on {PATH}"));
        });
    }
    
    private void OnDestroy() => _server.To.Close();
}

Env :
Windows 10, Unity 6000.0.41f1

[alec1o]

Hello! @Naokim-NHZ

Also, I don't understand why on the main page of the git, on the WebSocket sample section, we open the server twice, one time with an "http" address and a second time with a "ws" address. I've try it that way, but it won't work as well. I guess it's copy-paste mistake.

• True: had a documentation mistakes!

1. we use "http://" on server-side, I mean: Netly HTTP server also can receive HTTP RESTful request and WebSocket requests, so always ours server URI is over "http/s" e.g. HTTP.Server.To.Open("http://:").
2. we use "ws" or "wss" on client-side, client must say if want to connect to HTTP server as: "ws". "wss", "http", "https", so is reason why: sometimes looks confused. for Netly websocket we use "ws", except over HTTPS Proxy: like NGINX, APACHE... we can use "wss" on this case.
3. http path, before compile: looks that path of "ws / wss" URI match, e.g. "ws://127.0.0.1:7700/echo", needs your server run at "http://127.0.0.1:7700", and use. "HTTP.Map.WebSocket("/echo", (request, websocket) => { ... e.g. Debug.Log("Client Connected"); })".

[Naokim-NHZ]

Thanks for the quick answer, I greatly appreciate it. Sadly, it still doesn't work :( .

Although, there is other things I don't get from the main page sample :

• First, the server doesn't have any "WebSocketClients" property available. Idk, if that is an issue.

• Second, still on server part : there is one line to Open the server, and one to open the client ? Do we have to connect to the http server, then store the "client web socket" on the server and open the "echo" path afterward ? Once again, I've tried different setup and it always yield the "Can't connect" error.

[alec1o]

I'm sorry about "WebSocketClients" property missed. I didn't implement that, because I created prototype of API usage, just after programming that API, reason why: sometimes documentation resources is different than implemented resources. Now I'll go check your code on Netly Unity Project after see, if is a mistake or internal error and fix. and send you updated dll's or use updated source code. Wait for my quickly reply. See you later! 🫰

…

---- On dom, 13 jul 2025 23:34:27 +0200 ***@***.*** wrote ---- Thanks for the quick answer, I greatly appreciate it. Sadly, it still doesn't work :( . https://github.com/user-attachments/assets/f61a533f-8d50-4ac4-b141-1103f8de6c5e https://github.com/user-attachments/assets/cb292e9d-e7ce-4745-b9b3-aedeb00381de Although, there is other things I don't get from the main page sample : First, the server doesn't have any "WebSocketClients" property available. Idk, if that is an issue. https://github.com/user-attachments/assets/a82f0ee0-5ae5-4526-8fd4-dbce83e004ea Second, still on server part : there is one line to Open the server, and one to open the client ? Do we have to connect to the http server, then store the "client web socket" on the server and open the "echo" path afterward ? Once again, I've tried different setup and it always yield the "Can't connect" error. https://github.com/user-attachments/assets/549b7a70-85f8-4fe1-a6c0-5ccc362c7329 — Reply to this email directly, #100 (comment) , or https://github.com/notifications/unsubscribe-auth/AX7TDR6OKRHEZBJ2VCB7OO33ILGGHAVCNFSM6AAAAACBNLQJXKVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGNZUGU4TENI . You are receiving this because you commented.

[Naokim-NHZ]

Hello,

I've try to investigate further and I've find a lead, doing so :

• Same program in two .NET console program : Works perfectly 🆗
• Server is a .NET console program and Client is in Unity : Works perfectly 🆗
• Server is Unity and client is a .NET console program : Client failed to connect with error 404. No matter which Unity's target platform is used.
• The same Unity instance is both Server and client : Client unable to connect as in my first post.

So it seems the issue is Unity not being able to host the server. But it silently fails, since no exception are raised.
Maybe they limit connection somehow and there is a checkbox to tick somewhere.
Or maybe, because they have their own implementation of .NET dlls, they remove websocket features related to server hosting.

Anyway, Unity Transport Protocol (the thing they use for their new multiplayer solution) mention they use websocket under the hood. And that, on every platform, even WebGL.

Hope it can help.
Cheers !

[alec1o]

Hey. Thankful about you contribution. I'm so sorry I got so busy. I didn't investigate about this issue. But I'll investigate and solve that when time available... I need make it working on WebGL, what I think: someone @nvh2001 told me: alec1o/Byter#28 (comment) (WebGL) can't build dll, so I think build using mono, il2cpp, using Netly source code instead of dll. I'll try this things. but after try impl. raw websocket client, or maybe try using original dotnet dll... but I think it can work (unity side)

…

---- On ter, 15 jul 2025 17:54:34 +0200 ***@***.*** wrote ---- Hello, I've try to investigate further and I've find a lead, doing so : Same program in two .NET console program : Works perfectly 🆗 Server is a .NET console program and Client is in Unity : Works perfectly 🆗 Server is Unity and client is a .NET console program : Client failed to connect with error 404. No matter which Unity's target platform is used. So it seems the issue is Unity not being able to host the server. But it silently fails, since no exception are raised. Maybe they limit connection somehow and there is a checkbox to tick somewhere. Or maybe, because they have their own implementation of .NET dlls, they remove websocket features related to server hosting. Anyway, https://docs-multiplayer.unity3d.com/transport/current/minimal-workflow-ws/ (the thing they use for their new multiplayer solution) mention they use websocket under the hood. And that, on every platform, even WebGL. Hope, it can help. Cheers — Reply to this email directly, #100 (comment) , or https://github.com/notifications/unsubscribe-auth/AX7TDR7BJZ6SHXOUEGL5NVL3IUP3VAVCNFSM6AAAAACBNLQJXKVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGNZWGY3DINY . You are receiving this because you commented.