Websocket .net核心检测客户端何时断开互联网连接

Question

我在.net核心中使用websocket，我的问题是，当客户端不再连接到Internet时，他的websocket连接关闭，但是根据服务器，客户端仍处于连接状态，我没有收到任何断开连接数据包，另外，我正在Azure上发布Websocket，并且我已经设置了属性WebSocket = ON和AlwaysOn = On。请您能帮帮我！

我有以下服务器：

public async Task Invoke(HttpContext context)
{
  if (context.WebSockets.IsWebSocketRequest)
  {
    SocketUserObject socketUser = new SocketUserObject();
    if (_webSocketLogic.IsAuthorizedUser(context, ref socketUser, _operation))
    {
        var connection = await _webSocketHandler.OnConnected(context, socketUser, _operation);
        if (connection != null)
        {
            await _webSocketHandler.ListenConnection(connection);
        }
        else
        {
            context.Response.StatusCode = 404;
        }
    }
    else
    {
        context.Response.StatusCode = 404;
    }
}
}

 public async Task ListenConnection(WebSocketConnection connection)
 {
   var buffer = new byte[BufferSize];
   try
  {
    while (connection.WebSocket.State == WebSocketState.Open)
    {

        var result = await connection.WebSocket.ReceiveAsync(
             buffer: new ArraySegment<byte>(buffer),
             cancellationToken: CancellationToken.None);
        if (result.MessageType == WebSocketMessageType.Text)
        {
            var message = Encoding.UTF8.GetString(buffer, 0, result.Count);
            await ReceiveAsync(connection, message, _operation2);
        }
        else if (result.MessageType == WebSocketMessageType.Close)
        {
            await OnDisconnected(connection, _operation2);
        }
    }

}
catch (Exception ex)
{
    _logging.TraceError(ex, _operation);
}       
_logging.TraceLog(System.Reflection.MethodInfo.GetCurrentMethod(), _operation, "after State ", connection.WebSocket.State.ToString());
 }

我在启动中添加了以下内容：

    var webSocketOptions = new WebSocketOptions()
    {
        KeepAliveInterval = TimeSpan.FromSeconds(1),
        ReceiveBufferSize = 4 * 1024
    };
    app.UseWebSockets(webSocketOptions);

我还尝试将其添加到从Kudu控制台在Azure上创建的web.config文件中：

 <system.webServer>
    <webSocket  enabled="true"   receiveBufferLimit="4194304"  pingInterval="00:01:00">
   </webSocket>
 </system.webServer>

这是我的客户：

   public void StartReceiving(int modulo)
{
    RunWebSockets().GetAwaiter().GetResult();
}

private async Task RunWebSockets()
{
    var client = new ClientWebSocket();

    try
    {
        client.Options.SetRequestHeader("id_handset", "1");

        await client.ConnectAsync(new Uri(url), CancellationToken.None);

        Console.WriteLine("Connected!");

        var sending = Task.Run(async () =>
        {
            string line;
            if (client.State == WebSocketState.Open)
            {
                SocketOperation.Start(_socketOperation, client);
            }
        });

        var receiving = Receiving(client);

        await Task.WhenAll(sending, receiving);
    }
    catch (Exception ex)
    {
        if (client.State == WebSocketState.Open)
        {
            await client.CloseAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
        }
        SocketOperation.StopConsole();
        RunWebSockets().GetAwaiter().GetResult();
    }
}

private async Task Receiving(ClientWebSocket client)
{
    var buffer = new byte[1024 * 4];

    while (true)
    {
        var result = await client.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);

        if (result.MessageType == WebSocketMessageType.Text)
            Console.WriteLine(Encoding.UTF8.GetString(buffer, 0, result.Count));

        else if (result.MessageType == WebSocketMessageType.Close)
        {
            await client.CloseAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
            SocketOperation.StopConsole();
            RunWebSockets().GetAwaiter().GetResult();
            //await client.CloseOutputAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
            break;
        }
    }
}