WebSocketException: Unable to connect to the remote server

Question

I just started learning to write a server for my game with asp.net core.
I am trying to establish a websocket connection between the Unity game client and the asp.net core server.
I made a new asp.net core API project and added a new controller with this code in it.
(The code is copied from here)

namespace LazerbaseASPNET.Controllers  
{  
    public class BrianWebSocketController : ControllerBase  
    {  
        [HttpGet("/ws")]  
        public async Task Get()  
        {  
            System.Diagnostics.Trace.TraceError("WEBSOCKET!!! GET!!!    WEBSOCKET!!! GET!!!    WEBSOCKET!!! GET!!!    WEBSOCKET!!! GET!!!    ");  
            if (HttpContext.WebSockets.IsWebSocketRequest)  
            {  
                using var webSocket = await HttpContext.WebSockets.AcceptWebSocketAsync();  
                await Echo(webSocket);  
            }  
            else  
            {  
                HttpContext.Response.StatusCode = StatusCodes.Status400BadRequest;  
            }  
        }  
  
        private async Task Echo(WebSocket webSocket)  
        {  
            System.Diagnostics.Trace.TraceError("WEBSOCKET!!! ECHO!!!!!    WEBSOCKET!!! ECHO!!!!!    WEBSOCKET!!! ECHO!!!!!    WEBSOCKET!!! ECHO!!!!!    ");  
            var buffer = new byte[1024 * 4];  
            WebSocketReceiveResult result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);  
            while (!result.CloseStatus.HasValue)  
            {  
                await webSocket.SendAsync(new ArraySegment<byte>(buffer, 0, result.Count), result.MessageType, result.EndOfMessage, CancellationToken.None);  
                result = await webSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);  
            }  
            await webSocket.CloseAsync(result.CloseStatus.Value, result.CloseStatusDescription, CancellationToken.None);  
        }  
    }  
}  

Startup.cs looks like this (I added app.UseWebSockets();)

	public class Startup  
	{  
		public Startup(IConfiguration configuration)  
		{  
			Configuration = configuration;  
		}  

		public IConfiguration Configuration { get; }  

		// This method gets called by the runtime. Use this method to add services to the container.  
		public void ConfigureServices(IServiceCollection services)  
		{  
			services.AddControllers();  
		}  

		// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.  
		public void Configure(IApplicationBuilder app, IWebHostEnvironment env)  
		{  
			if (env.IsDevelopment())  
			{  
				app.UseDeveloperExceptionPage();  
			}  
			app.UseWebSockets();  
			app.UseHttpsRedirection();  
			app.UseRouting();  
			app.UseAuthorization();  
			app.UseEndpoints(endpoints =>  
			{  
				endpoints.MapControllers();  
			});  
		}  
	}  

In the Unity client I have the following code...

  public async Task Connect ()   
    {        
        _socket = new ClientWebSocket();  
        Uri uri = new Uri(@"ws://localhost:44348/ws");     
        Debug.Log("start connecting websocket");  
        await _socket.ConnectAsync(uri, CancellationToken.None);  
        Debug.Log("finished connecting websocket");  
        Listen();  
    }  

I press the run with IIS express button in visual studio, which opens a browser window at the local server, the address is https://localhost:44348.
Then I leave that browser open and run the code above in Unity.. Unity never gets to this second debug line.. Debug.Log("finished connecting websocket");
Also in the asp.net program visual studio output window I never see the WEBSOCKET!!! GET!!! log.

I get this error in Unity

WebSocketException: Unable to connect to the remote server  
System.Net.WebSockets.WebSocketHandle+<ParseAndValidateConnectResponseAsync>d__28.MoveNext () (at <5a2009c85b134970925993880e2ecb2e>:0)  

I have also tried publishing the asp.net program to azure and trying the url there, but I still never see the second debug.log in Unity.

I reckon my Unity code is fine as the same code is able to establish a socket connection and send and receive data from a node.js server I have on Heroku. I just have to change the url.

What am I doing wrong? Thanks!

Answer 1

what version of windows are you using? be sure your version of IIS Express supports web sockets.

Answer 2

So I got this working. There were two issues

1. when I added these two attributes to my controller class with the sockets code in it, then I could successfully make a socket connection to server running locally from visual studio on my machine.

    [ApiController]  
    [Route("[controller]")]  
    public class BrianWebSocketController : ControllerBase  
    {  
   

2. It still did not work with the published version on azure however.. I searched all the options on azure and eventually found an option for websockets buried in there. It was turned off by default, so I turned it on and then I was able to make a connection to the server from Unity.