WebSocket4Net - websocket上接收的“返回”消息

Question

我正在使用WebSocket4Net与服务器通信我的xamarin android应用程序。我可以从我的应用程序发送和接收消息，但我不知道如何在我的发送方法中获得传入消息(在webSocket_MessageReceived中接收)。我在谷歌上搜索如何使用回调来实现它，但无法实现。任何帮助都是非常感谢的。

这是在我的WebSocketHelper类中：

        private WebSocket webSocket;
        private string outgoingMessage;

        public WebSocketHelper(string url)
        {
            webSocket = new WebSocket(url);
            webSocket.Opened += new EventHandler((sender, e) => webSocket_Opened(sender, e, this.outgoingMessage));
            webSocket.Error += new EventHandler<SuperSocket.ClientEngine.ErrorEventArgs>(webSocket_Error);
            //webSocket.Closed += new EventHandler(webSocket_Closed);
            webSocket.MessageReceived += new EventHandler<MessageReceivedEventArgs>(webSocket_MessageReceived);
        }

        public string Send(string message)
        {
            this.outgoingMessage = message;

            webSocket.Open();

            //Get message received from websocket to return it

            return ""; //TEMP return
        }

        private void webSocket_Opened(object sender, EventArgs e, string message)
        {
            webSocket.Send(message);
        }

        private void webSocket_Error(object sender, SuperSocket.ClientEngine.ErrorEventArgs e)
        {
            string errorMessage = e.Exception.Message;

            //return errorMessage to Send method (not sure), this is secondary
        }

        private void webSocket_MessageReceived(object sender, MessageReceivedEventArgs e)
        {
            string incomingMessage = e.Message;

            //I need to return incomingMessage to Send method
        }

Answer 1

你必须做两件事：

1. 引入类型为WebSocketHelper的string成员，您将通过该成员将字符串值从事件处理程序webSocket_MessageReceived传递给另一个方法(Send)
2. 使Send等待直到调用webSocket_MessageReceived处理程序。您可以使用AutoResetEvent (它应该可以在Xamarin库中使用)。

请注意，_messageReceivedEvent.WaitOne会阻塞您的Send方法，因此如果您从UI事件处理程序调用此方法，则在调用_messageReceivedEvent.Set之前，UI将无法响应。考虑重新设计这个类，以便使用异步方法(它可以公开UI订阅的事件MessageReceivedEvent .)。

    public class WebSocketHelper : IDisposable
    {
       private string _incomingMessage;
       private AutoResetEvent _messageReceivedEvent = new AutoResetEvent(false);
       ...

       public string Send(string message)
       {
          this.outgoingMessage = message;
          webSocket.Open();
          this._messageReceivedEvent.WaitOne(); 
          return this._incomingMessage; 
       }

       private void webSocket_MessageReceived(object sender, MessageReceivedEventArgs e)
       {
          this._incomingMessage = e.Message;
          this._messageReceivedEvent.Set();
       }

       ...
    }