ASP.. NET在向客户端发送所有websocket数据之前关闭连接

我写了一个简单的asp.net websocket处理程序作为远程数据处理服务器和客户端之间的网关。我在我的本地机器(win8, IIS EXPRESS 8)上进行了测试，一切都运行良好。但是在azure网站中，ASP。. NET在向客户端发送所有websocket数据之前关闭连接。

以下是我的数据传输代码:

internal class WebSocketStreamTransfer{
    public WebSocketStreamTransfer(CancellationToken disconnectionToken){
        DisconnectionToken = disconnectionToken;
    }
    private CancellationToken DisconnectionToken{
        get;
        set;
    }
    public async Task AcceptWebSocketConnection(WebSocketContext context) {
        if (context == null)
            throw new ArgumentNullException("context");
        WebSocket websocket = context.WebSocket;
        if (websocket == null)
            throw new SocksOverHttpException("Null websocket");
        using(IConnection conn = ConnectionManagerFactory.ConnectionManager.CreateConnection(Guid.NewGuid().ToString())) {
            try {
                DisconnectionToken.Register(conn.Close);
                TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>(null);
                await Task.WhenAny(SendDataToRemoteServer(conn, websocket, DisconnectionToken, tcs), SendDataToClient(conn, websocket, DisconnectionToken, tcs.Task));
            } catch(Exception e) {
                Logger.LogException(e);
            }
        }
    }
    internal static async Task SendDataToRemoteServer(IConnection conn, WebSocket websocket, CancellationToken cancelToken, TaskCompletionSource<bool> tcs) {
        try {
            ArraySegment<byte> buffer = new ArraySegment<byte>(new byte[ApplicationConfiguration.GetDefaultBufferSize()]);
            while (IsConnected(conn, cancelToken, websocket)) {
                WebSocketReceiveResult result = await websocket.ReceiveAsync(buffer, cancelToken);
                if (websocket.State == WebSocketState.Open) {
                    if (result.MessageType == WebSocketMessageType.Binary) {
                        if (result.Count > 0) {
                            if (IsConnected(conn, cancelToken, websocket)) {
                                int numRead = await conn.SendData(buffer.Array, 0, result.Count, cancelToken);
                                if (numRead > 0) {
                                    tcs.TrySetResult(true); // Notify SendDataToClient can continue
                                }else{
                                    Logger.LogError("Client not send enough data for remote connection built");
                                    return;
                                }
                            } else {
                                Logger.LogInformation("SendDataToRemoteServer: Cancel send data to remote server due to connection closed");
                            }
                        } else
                            Logger.LogInformation("Receive empty binary message");
                    } else if (result.MessageType == WebSocketMessageType.Text) {
                        Logger.LogError("Receive unexpected text message");
                        return;
                    } else {
                        Logger.LogInformation("Receive close message");
                        await websocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Close Connection", cancelToken);
                        return;
                    }
                } else {
                    Logger.LogInformation("SendDataToRemoteServer: WebSocket connection closed by client");
                    return;
                }
            }
        }finally{
            tcs.TrySetResult(true);
        }
    }
    internal static async Task SendDataToClient(IConnection conn, WebSocket websocket, CancellationToken cancelToken, Task connectedTask) {
        await connectedTask;
        while (IsConnected(conn, cancelToken, websocket)) {
            byte[] data = await conn.ReceiveData(cancelToken);
            if (data.Length <= 0) {
                Logger.LogInformation("SendDataToClient: Get empty data from remote server");
                return;
            }
            if (IsConnected(conn, cancelToken, websocket)) {
                await websocket.SendAsync(new ArraySegment<byte>(data), WebSocketMessageType.Binary, true, cancelToken);
            } else {
                Logger.LogInformation("SendDataToClient: Cancel send data to client due to connection closed");
            }
        }
    }
    internal static bool IsConnected(IConnection conn, CancellationToken cancelToken, WebSocket websocket) {
        bool socketConnected = websocket.State == WebSocketState.Open;
        return socketConnected && conn.Connected && !cancelToken.IsCancellationRequested;
    }
}

问题场景:

SendDataToRemoteServer等待客户端数据，客户端还没有数据要发送
SendDataToClient从远程服务器接收到空数据，表示远程服务器开始关闭连接。所以完成SendDataToClient
AcceptWebSocketConnection finish because Task.WhenAny(SendDataToRemoteServer(conn, websocket, DisconnectionToken, tcs), SendDataToClient(conn, websocket, DisconnectionToken, tcs.Task))
期待ASP。. NET在关闭tcp连接之前发送所有数据。. NET立即关闭连接

WebSocket消息可以分成不同的帧。您没有检查消息是否已完成。从WS连接向其他连接发送信息的代码应该如下所示:

WebSocketReceiveResult result = null;
do
{
    result = await source.ReceiveAsync(buffer, CancellationToken.None);
    var sendBuffer = new ArraySegment<Byte>(buffer.Array, buffer.Offset, result.Count);
    await target.SendAsync(sendBuffer, result.MessageType, result.EndOfMessage, CancellationToken.None);
}
while (!result.EndOfMessage);

您必须检查EndOfMessage属性，并在消息未完成时继续阅读。

它在您的本地计算机上工作，因为您在本地不受相同方式的缓冲的影响，或者因为您正在尝试的消息更小。

await Task.WhenAny等待任务完成。当SendDataToRemoteServer任务完成时，不等待SendDataToClient任务完成。

你需要改变

await Task.WhenAny(SendDataToRemoteServer(conn, websocket, DisconnectionToken, tcs), SendDataToClient(conn, websocket, DisconnectionToken, tcs.Task));

await Task.WhenAll(SendDataToRemoteServer(conn, websocket, DisconnectionToken, tcs), SendDataToClient(conn, websocket, DisconnectionToken, tcs.Task));

小样本:

async Task t1()
{
    await Task.Delay(1000);
}
async Task t2()
{
    await Task.Delay(2000);
}
Stopwatch watch = new Stopwatch();
watch.Start();
await Task.WhenAny(t1(), t2());
watch.Stop();
Debug.WriteLine("total milliseconds {0}", watch.ElapsedMilliseconds); // total milliseconds 1007

Stopwatch watch = new Stopwatch();
watch.Start();
await Task.WhenAll(t1(), t2());
watch.Stop();
Debug.WriteLine("total milliseconds {0}", watch.ElapsedMilliseconds); // total milliseconds 2009

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