为什么火币服务器收不到 C# WebSocket Ping？

Question

我正在尝试从火币 USDT 掉期传输比特币价格，但我的 ping/pong 机制无法正常工作，因此火币总是在 30 秒后关闭连接。

这就是文档所说的https://huobiapi.github.io/docs/usdt_swap/v1/en/#market-heartbeat：

WebSocket API 支持双向心跳。 Server 和 Client 都可以发送 ping 消息，对方可以用 pong 消息返回。

WebSocket Server 发送心跳： {“平”：18212558000}

WebSocket 客户端应该响应： {“乒乓”：18212558000}

注意：一旦 WebSocket 客户端和 WebSocket 服务器建立连接，服务器将每 5 秒发送一次心跳（频率可能会改变）。如果 WebSocket 客户端 5 次忽略心跳消息，连接将自动断开。如果 WebSocket 客户端在最近的 2 个心跳消息中响应一个“ping”值，服务器将保持连接。

using System;
using System.IO;
using System.IO.Compression;
using System.Net.WebSockets;
using System.Text;
using System.Threading;

namespace HuobiMarketWebSocketTest
{
    class HuobiMarketWebSocketTest
    {
        public static void Main(string[] args)
        {
            int pings = 0;
            ClientWebSocket ClientWebSocket = new ClientWebSocket();
            string symbol = "btcusdt";
            ClientWebSocket.ConnectAsync(new Uri("wss://api.hbdm.com/linear-swap-ws"), CancellationToken.None).Wait();

            try
            {
                // Subscribe to BTC
                string subscribeTrade = $"{{ \"sub\": \"market.{symbol}.trade.detail\", \"id\": \"{symbol} trade\"}}";
                byte[] subscribeTradeAsBytes = Encoding.UTF8.GetBytes(subscribeTrade);
                ClientWebSocket.SendAsync(subscribeTradeAsBytes, WebSocketMessageType.Text, true, CancellationToken.None).Wait();
                Console.WriteLine($"{subscribeTrade} sent.");

                string subscribeQuote = $"{{ \"sub\": \"market.{symbol}.bbo\", \"id\": \"{symbol} bbo\"}}";
                byte[] subscribeQuoteAsBytes = Encoding.UTF8.GetBytes(subscribeQuote);
                ClientWebSocket.SendAsync(subscribeQuoteAsBytes, WebSocketMessageType.Text, true, CancellationToken.None).Wait();
                Console.WriteLine($"{subscribeQuote} sent.");

                ArraySegment<byte> bytesReceived = new ArraySegment<byte>(new byte[819200]);

                //Read from WebSocket
                while (ClientWebSocket.State == WebSocketState.Open)
                {
                    WebSocketReceiveResult receiveResult = ClientWebSocket.ReceiveAsync(bytesReceived, CancellationToken.None).Result;
                    byte[] compressedBytes = bytesReceived.Array[..receiveResult.Count];
                    byte[] decompressedBytes;

                    //Decompress json
                    using (MemoryStream compressedStream = new MemoryStream(compressedBytes))
                    {
                        using (GZipStream decompressionStream = new GZipStream(compressedStream, CompressionMode.Decompress))
                        {
                            using (MemoryStream decompressedStream = new MemoryStream())
                            {
                                decompressionStream.CopyTo(decompressedStream);
                                decompressedBytes = decompressedStream.ToArray();
                            }
                        }
                    }
                    string json = Encoding.UTF8.GetString(decompressedBytes);

                    // Handle ping
                    if (json.Contains("ping"))
                    {
                        pings++;
                        string pong = json.Replace("ping", "pong");
                        Console.WriteLine($"{json} received");
                        byte[] pongAsBytes = Encoding.UTF8.GetBytes(pong);
                        ClientWebSocket.SendAsync(pongAsBytes, WebSocketMessageType.Text, true, CancellationToken.None).Wait();
                        Console.WriteLine($"{pong} sent");
                        Console.WriteLine($"{pings} pings received");
                    }
                    else
                    {
                        // Uncomment to see that subscription worked
                        //Console.WriteLine(json);
                    }
                }
            }
            catch (Exception exception)
            {
                Console.WriteLine(exception);

                Console.WriteLine($"Huobi closed WebSocket after {pings} pings.");
            }
        }
    }
}

这是我的程序的输出：

{ "sub": "market.btcusdt.trade.detail", "id": "btcusdt trade"} sent.
{ "sub": "market.btcusdt.bbo", "id": "btcusdt bbo"} sent.
{"ping":1627090272242} received
{"pong":1627090272242} sent
1 pings received
{"ping":1627090277234} received
{"pong":1627090277234} sent
2 pings received
{"ping":1627090282238} received
{"pong":1627090282238} sent
3 pings received
{"ping":1627090287239} received
{"pong":1627090287239} sent
4 pings received
{"ping":1627090292238} received
{"pong":1627090292238} sent
5 pings received
{"ping":1627090297241} received
{"pong":1627090297241} sent
6 pings received
System.AggregateException: One or more errors occurred. (The remote party closed the WebSocket connection without completing the close handshake.)
 ---> System.Net.WebSockets.WebSocketException (0x80004005): The remote party closed the WebSocket connection without completing the close handshake.
   at System.Net.WebSockets.ManagedWebSocket.ThrowIfEOFUnexpected(Boolean throwOnPrematureClosure)
   at System.Net.WebSockets.ManagedWebSocket.EnsureBufferContainsAsync(Int32 minimumRequiredBytes, CancellationToken cancellationToken, Boolean throwOnPrematureClosure)
   at System.Net.WebSockets.ManagedWebSocket.ReceiveAsyncPrivate[TWebSocketReceiveResultGetter,TWebSocketReceiveResult](Memory`1 payloadBuffer, CancellationToken cancellationToken, TWebSocketReceiveResultGetter resultGetter)
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at System.Threading.Tasks.Task`1.get_Result()
   at HuobiMarketWebSocketTest.HuobiMarketWebSocketTest.Main(String[] args) in C:\home\source\csharp\prog\HuobiMarketWebSocketTest - pong not recieved\HuobiMarketWebSocketTest\HuobiMarketWebSocketTest\HuobiMarketWebSocketTest.cs:line 156
Huobi closed WebSocket after 6 pings.

Answer 1

发生断开连接是因为 .NET ClientWebsocket 在内部使用 ManagedWebSocket，它会发送一个未经请求的 pong 帧作为其保持活动处理的一部分。根据 websocket 标准，这是正确的行为。但是，它似乎会导致火币的期货和掉期服务器出现问题（但不是现货）。如果将 ClientwebSocket.Options.KeepAliveInterval 设置为 TimeSpan.Zero，则可以避免 ManagedWebSocket 创建保活计时器，从而停止设置未经请求的 pong 帧。这样做的缺点是会话从 2 向心跳变为 1 向心跳，但由于在应用程序级别存在心跳，因此这里没有真正的缺点。