websocket-api-controller-example

This is an example WebSocket server API with ASP.NET Core MVC approach. The WebSocket server is implemented in a Controller class, in the same way as a standard REST controller is usually implemented.

Separate controller is thin, unit testable and more readable than middleware. If the request is not a WebSocket request (is missing web socket upgrade headers) then 400 is returned.

This is an excerpt from the controller class:

    [Route("/api/ws")]
    [ApiController]
    public class WebSocketApiController : ControllerBase
    {
        ...

        [HttpGet]
        public async Task<IActionResult> Get()
        {
            var context = ControllerContext.HttpContext;

            if (context.WebSockets.IsWebSocketRequest)
            {
                var webSocket = await context.WebSockets.AcceptWebSocketAsync();
                Console.WriteLine($"Accepted connection '{context.Connection.Id}'");
                var connection = _connectionFactory.CreateConnection(webSocket);
                await _connectionManager.HandleConnection(connection);

                return new EmptyResult();
            }
            else
            {
                return new StatusCodeResult((int) HttpStatusCode.BadRequest);
            }
        }
    }

The server listens for messages from clients and responds to each message with the same message (echo)
The server listens for messages on ws://localhost:5000/api/ws and wss://localhost:5001/api/ws\

The WebSocket instance is wrapped by the WebSocketConnection class that exposes standard WebSocket methods like Receive, Send, Close. The class is separately testable and keeps the websocket logic away from Controller.

The solution is fully asynchronous and nonblocking.

Additionally the solution features the AddControllersAsServices approach which means the Controller classes are created in code and not by framework.