// Order of operations:
// 1. A WebSocket handshake request is received by the middleware.
// 2. The middleware inserts an alternate Accept signature into the OWIN environment.
// 3. The middleware invokes Next and stores Next's Task locally. It then returns an alternate Task to the server.
// 4. The OwinFeatureCollection adapts the alternate Accept signature to IHttpWebSocketFeature.AcceptAsync.
// 5. A component later in the pipleline invokes IHttpWebSocketFeature.AcceptAsync (mapped to AcceptWebSocketAsync).
// 6. The middleware calls the OWIN Accept, providing a local callback, and returns an incomplete Task.
// 7. The middleware completes the alternate Task it returned from Invoke, telling the server that the request pipeline has completed.
// 8. The server invokes the middleware's callback, which creats a WebSocket adapter complete's the orriginal Accept Task with it.
// 9. The middleware waits while the application uses the WebSocket, where the end is signaled by the Next's Task completion.
public static AppFunc AdaptWebSockets(AppFunc next)
{
return(environment =>
{
object accept;
if (environment.TryGetValue(OwinConstants.WebSocket.Accept, out accept) && accept is WebSocketAccept)
{
var adapter = new OwinWebSocketAcceptAdapter((WebSocketAccept)accept);
environment[OwinConstants.WebSocket.AcceptAlt] = new WebSocketAcceptAlt(adapter.AcceptWebSocketAsync);
try
{
adapter.UpstreamTask = next(environment);
adapter.UpstreamWentAsyncTcs.TrySetResult(0);
adapter.UpstreamTask.ContinueWith(adapter.EnsureCompleted, TaskContinuationOptions.ExecuteSynchronously);
}
catch (Exception ex)
{
adapter.UpstreamWentAsyncTcs.TrySetException(ex);
throw;
}
return adapter.RequestTask;
}
else
{
return next(environment);
}
});
}
// Order of operations:
// 1. A WebSocket handshake request is received by the middleware.
// 2. The middleware inserts an alternate Accept signature into the OWIN environment.
// 3. The middleware invokes Next and stores Next's Task locally. It then returns an alternate Task to the server.
// 4. The OwinFeatureCollection adapts the alternate Accept signature to IHttpWebSocketFeature.AcceptAsync.
// 5. A component later in the pipleline invokes IHttpWebSocketFeature.AcceptAsync (mapped to AcceptWebSocketAsync).
// 6. The middleware calls the OWIN Accept, providing a local callback, and returns an incomplete Task.
// 7. The middleware completes the alternate Task it returned from Invoke, telling the server that the request pipeline has completed.
// 8. The server invokes the middleware's callback, which creats a WebSocket adapter complete's the orriginal Accept Task with it.
// 9. The middleware waits while the application uses the WebSocket, where the end is signaled by the Next's Task completion.
public static AppFunc AdaptWebSockets(AppFunc next)
{
return environment =>
{
object accept;
if (environment.TryGetValue(OwinConstants.WebSocket.Accept, out accept) && accept is WebSocketAccept)
{
var adapter = new OwinWebSocketAcceptAdapter((WebSocketAccept)accept);
environment[OwinConstants.WebSocket.AcceptAlt] = new WebSocketAcceptAlt(adapter.AcceptWebSocketAsync);
try
{
adapter.UpstreamTask = next(environment);
adapter.UpstreamWentAsyncTcs.TrySetResult(0);
adapter.UpstreamTask.ContinueWith(adapter.EnsureCompleted, TaskContinuationOptions.ExecuteSynchronously);
}
catch (Exception ex)
{
adapter.UpstreamWentAsyncTcs.TrySetException(ex);
throw;
}
return adapter.RequestTask;
}
else
{
return next(environment);
}
};
}