如何使用WebSocketSharp发出类似同步的websocket请求？

Question

我在做C#项目。我想通过websocketsharp库以某种同步的方式发送API请求。

我一直试着按照以下方式去做：

>

在发送任何WS请求之前，我们使用唯一的ID创建新的SynchronousRequest（）对象，并将新创建的对象添加到某种类型的等待列表中

我们在响应中发送WS请求，向有效负载添加唯一的ID-服务器将返回相同的ID。

我们开始等待事件发出信号（一旦我们收到响应就会发出信号）

在响应处理程序上：

问题是第3步，一旦我在事件上使用WaitOne（），整个websocket客户机就挂起了，并且不会收到进一步的响应--导致完全死锁。

我如何在单独的线程中执行某种WaitOne（）调用，或者可能有完全更好的解决方案来解决我的问题，从而使整个客户端不会挂起，并且我们匹配上下文？

public class SynchronousRequest
{
    public long requestId;
    public ManualResetEvent resetEvent = new ManualResetEvent(false);
    public dynamic response;

    public SynchronousRequest()
    {
        var random = new Random();
        requestId = random.Next();
    }

}


public class APIWebSocket: BaseAPIWebSocket
{


    private List<SynchronousRequest> waitingSyncRequests = new List<SynchronousRequest>();


    public APIWebSocket()
    {
        ws = new WebSocket("wss://www.someserver.com");

        registerConnectionEvents(); //Registers onOpen(), onMessage() handlers and similar
    }



    public void SendSyncTest()
    {
        var sr = new SynchronousRequest();
        waitingSyncRequests.Add(sr);

        //some data to send
        var msg = new
        {
            jsonrpc = "2.0",
            method = "public/ticker",
            id = sr.requestId, //Response should contain the same ID
            @params = new
            {
                instrument_name = "ETH"
            }
        };

        ws.Send(JsonConvert.SerializeObject(msg));

        //Below WaitOne() causes the entire websocket connection/thread to block
        // No further messages will be received by HandleMessage() once we call WaitOne()

        sr.resetEvent.WaitOne(); //Wait until we receive notification that response has been received

        //do some processing on response here... 

       //Synchronous request completed, remove it from list
       waitingSyncRequests.Remove(sr);
    }




    protected override void OnReceivedMessage(System.Object sender, WebSocketSharp.MessageEventArgs e)
    {
        dynamic message = JsonConvert.DeserializeObject(e.Data);

        if (message.id != null )
        {
            //Find a resetEvent for given message.id
            var matchingSyncRequest = waitingSyncRequests.First(r => r.requestId == message.id);
            if (matchingSyncRequest != null)
            {
                matchingSyncRequest.response = message;
                matchingSyncRequest.resetEvent.Set(); //Notify that response has been received
            }
        }

    }

}

Answer 1

根据我的理解，对于将在将来某个时间设置的某个事件，您需要await。您可以考虑使用TaskCompletionSource。

>

1.每当您发送需要其结果的消息时，您可以创建TaskCompletionSource(tcs)，将其添加到Dictionary并通过套接字发送消息。

2.您在TCS上等待tcs.task或tcs.task.result。

3.在另一个线程/任务上，您可以处理传入的响应（在您的情况下，您有您的received message Handler。每当您接收到目标类型或id的响应时，您可以根据id从字典中提取TCS和Task.setResult(response)。这时，调用方（您正在等待的调用方）将被解除阻止。

 public class Message
 {
   public string ID{get;set;}
 }
 public class Response
 {
     public string Id{get;set;}
 }

 public void MyClass
 {
    private ConcurrentDictionary<string,TaskCompletionSource<Response>>map=new ConcurrentDictionary<string,TaskCompletionSource<Response>>();
    private Websocket socket;
    public void SomeEventTrigger()
    {
        var msg=new Message{ Id="somespecialID" };
        var tcs=new TaskCompletionSource<Response>();
        ws.Send(JsonConvert.SerializeObject(msg));
        if(!this.map.TryAdd(msg.Id,tcs))
        {
           return;
        }
        var result=tcs.Result; //this gets blocked until you use `tcs.SetResult`- >  that would happen in your OnReceivedMessage  
        this.map.TryRemove(msg.Id,out TaskCompletionSource<Response>resp);

    }
    protected override void OnReceivedMessage(System.Object sender, WebSocketSharp.MessageEventArgs e)
    {
         Response message = JsonConvert.DeserializeObject<Response>(e.Data);

         if (message.id != null )
         {

             if(this.map.TryGetValue(message.id),out TaskCompletionSource<Response> tcs)
             {
                tcs.SetResult(message); //this unblocks the method that wrote the message to the socket   (above)
             }


         }
      }
   }

p.s您需要确保在正确的TCS上使用Task.SetResult，以便对SomeEventTrigger方法的正确调用停止等待。