public async Task BroadcastLoopAsync()
{
var cancellationToken = BroadcastLoopTokenSource.Token;
while (!cancellationToken.IsCancellationRequested)
{
try
{
await Task.Delay(WebSocketsUtils.BROADCAST_TRANSMIT_INTERVAL_MS, cancellationToken);
if (!cancellationToken.IsCancellationRequested && Socket.State == WebSocketState.Open && BroadcastQueue.TryTake(out var message))
{
Console.WriteLine($"Socket {SocketId}: Sending from queue.");
var msgbuf = new ArraySegment <byte>(Encoding.UTF8.GetBytes(message));
await Socket.SendAsync(msgbuf, WebSocketMessageType.Text, endOfMessage : true, CancellationToken.None);
}
}
catch (OperationCanceledException)
{
// normal upon task/token cancellation, disregard
}
catch (Exception ex)
{
WebSocketsUtils.ReportException(ex);
}
}
}
// use dependency injection to grab a reference to the hosting container's lifetime cancellation tokens
//public WebSocketMiddleware(IHostApplicationLifetime hostLifetime)
//{
// // gracefully close all websockets during shutdown (only register on first instantiation)
// if (AppShutdownHandler.Token.Equals(CancellationToken.None))
// AppShutdownHandler = hostLifetime.ApplicationStopping.Register(ApplicationShutdownHandler);
//}
public async Task InvokeAsync(HttpContext context, RequestDelegate next)
{
try
{
if (ServerIsRunning)
{
if (context.WebSockets.IsWebSocketRequest)
{
int socketId = Interlocked.Increment(ref SocketCounter);
var socket = await context.WebSockets.AcceptWebSocketAsync();
var completion = new TaskCompletionSource <object>();
var client = new ConnectedClient(socketId, socket, completion);
Clients.TryAdd(socketId, client);
Console.WriteLine($"Socket {socketId}: New connection.");
// TaskCompletionSource<> is used to keep the middleware pipeline alive;
// SocketProcessingLoop calls TrySetResult upon socket termination
_ = Task.Run(() => SocketProcessingLoopAsync(client).ConfigureAwait(false));
await completion.Task;
}
else
{
if (context.Request.Headers["Accept"][0].Contains("text/html"))
{
Console.WriteLine("Sending HTML to client.");
await context.Response.WriteAsync(SimpleHtmlClient.HTML);
}
else
{
// ignore other requests (such as favicon)
// potentially other middleware will handle it (see finally block)
}
}
}
else
{
// ServerIsRunning = false
// HTTP 409 Conflict (with server's current state)
context.Response.StatusCode = 409;
}
}
catch (Exception ex)
{
// HTTP 500 Internal server error
context.Response.StatusCode = 500;
WebSocketsUtils.ReportException(ex);
}
finally
{
// if this middleware didn't handle the request, pass it on
if (!context.Response.HasStarted)
{
await next(context);
}
}
}
private static async Task CloseAllSocketsAsync()
{
// We can't dispose the sockets until the processing loops are terminated,
// but terminating the loops will abort the sockets, preventing graceful closing.
var disposeQueue = new List <WebSocket>(Clients.Count);
while (Clients.Count > 0)
{
var client = Clients.ElementAt(0).Value;
Console.WriteLine($"Closing Socket {client.SocketId}");
Console.WriteLine("... ending broadcast loop");
client.BroadcastLoopTokenSource.Cancel();
if (client.Socket.State != WebSocketState.Open)
{
Console.WriteLine($"... socket not open, state = {client.Socket.State}");
}
else
{
var timeout = new CancellationTokenSource(WebSocketsUtils.CLOSE_SOCKET_TIMEOUT_MS);
try
{
Console.WriteLine("... starting close handshake");
await client.Socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closing", timeout.Token);
}
catch (OperationCanceledException ex)
{
WebSocketsUtils.ReportException(ex);
// normal upon task/token cancellation, disregard
}
}
if (Clients.TryRemove(client.SocketId, out _))
{
// only safe to Dispose once, so only add it if this loop can't process it again
disposeQueue.Add(client.Socket);
}
Console.WriteLine("... done");
}
// now that they're all closed, terminate the blocking ReceiveAsync calls in the SocketProcessingLoop threads
SocketLoopTokenSource.Cancel();
// dispose all resources
foreach (var socket in disposeQueue)
{
socket.Dispose();
}
}
private static async Task SocketProcessingLoopAsync(ConnectedClient client)
{
_ = Task.Run(() => client.BroadcastLoopAsync().ConfigureAwait(false));
var socket = client.Socket;
var loopToken = SocketLoopTokenSource.Token;
var broadcastTokenSource = client.BroadcastLoopTokenSource; // store a copy for use in finally block
try
{
var buffer = WebSocket.CreateServerBuffer(4096);
while (socket.State != WebSocketState.Closed && socket.State != WebSocketState.Aborted && !loopToken.IsCancellationRequested)
{
var receiveResult = await client.Socket.ReceiveAsync(buffer, loopToken);
// if the token is cancelled while ReceiveAsync is blocking, the socket state changes to aborted and it can't be used
if (!loopToken.IsCancellationRequested)
{
// the client is notifying us that the connection will close; send acknowledgement
if (client.Socket.State == WebSocketState.CloseReceived && receiveResult.MessageType == WebSocketMessageType.Close)
{
Console.WriteLine($"Socket {client.SocketId}: Acknowledging Close frame received from client");
broadcastTokenSource.Cancel();
await socket.CloseOutputAsync(WebSocketCloseStatus.NormalClosure, "Acknowledge Close frame", CancellationToken.None);
// the socket state changes to closed at this point
}
// echo text or binary data to the broadcast queue
if (client.Socket.State == WebSocketState.Open)
{
Console.WriteLine($"Socket {client.SocketId}: Received {receiveResult.MessageType} frame ({receiveResult.Count} bytes).");
Console.WriteLine($"Socket {client.SocketId}: Echoing data to queue.");
string message = Encoding.UTF8.GetString(buffer.Array, 0, receiveResult.Count);
BroadcastPrice(message);
//ECHO: client.BroadcastQueue.Add(message);
}
}
}
}
catch (OperationCanceledException)
{
// normal upon task/token cancellation, disregard
}
catch (Exception ex)
{
Console.WriteLine($"Socket {client.SocketId}:");
WebSocketsUtils.ReportException(ex);
}
finally
{
broadcastTokenSource.Cancel();
Console.WriteLine($"Socket {client.SocketId}: Ended processing loop in state {socket.State}");
// don't leave the socket in any potentially connected state
if (client.Socket.State != WebSocketState.Closed)
{
client.Socket.Abort();
}
// by this point the socket is closed or aborted, the ConnectedClient object is useless
if (Clients.TryRemove(client.SocketId, out _))
{
socket.Dispose();
}
// signal to the middleware pipeline that this task has completed
client.TaskCompletion.SetResult(true);
}
}
