c# - 使用 Newtonsoft.Json 从网络流中反序列化数据挂起

Question

使用 JsonSerializer 通过套接字接收的数据:

var stream = new NetworkStream(socket);
var serializer = new JsonSerializer();

using (var sr = new StreamReader(stream, new UTF8Encoding(), false))
using (var jsonTextReader = new JsonTextReader(sr))
{
    var result = serializer.Deserialize(jsonTextReader).ToString();                
}

但是当从套接字接收到的数据长度约为 2890 字节时，对 Deserialize 的调用挂起。

可以使用此代码轻松重现(当 jsonArrayElementsCount = 192 - 好的，当 193 - 它挂起):

using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using Newtonsoft.Json;

namespace JsonNetHangsTest
{
    class Program
    {
        static void Main(string[] args)
        {
            const int port = 11999;
            const int jsonArrayElementsCount = 193;

            var serverStartedEvent = new ManualResetEvent(false);
            var clientReceivedEvent = new ManualResetEvent(false);

#region server
            ThreadPool.QueueUserWorkItem(work =>
            {
                var server = new TcpListener(IPAddress.Parse("0.0.0.0"), port);
                server.Start();

                serverStartedEvent.Set();

                var serverSocket = server.AcceptSocket();

                var jsonString = "[\r\n" + String.Join(",", Enumerable.Repeat("  \"testdata\"\r\n", jsonArrayElementsCount)) + "]";
                var bytes = new UTF8Encoding().GetBytes(jsonString);
                serverSocket.Send(bytes);
                Console.WriteLine("server send: " + bytes.Length);

                clientReceivedEvent.WaitOne();

            });
#endregion

            serverStartedEvent.WaitOne();

            var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            socket.Connect("127.0.0.1", port);

            var stream = new NetworkStream(socket);
            var serializer = new JsonSerializer();

            using (var sr = new StreamReader(stream, new UTF8Encoding(), false))
            using (var jsonTextReader = new JsonTextReader(sr))
            {
                var result = serializer.Deserialize(jsonTextReader).ToString();
                Console.WriteLine("client receive: " + new UTF8Encoding().GetBytes(result).Length);
            }

            clientReceivedEvent.Set();
            Console.ReadKey();
        }
    }
}

我在这里错过了什么？

Answer 1

您的问题是您发送的 JSON 的尾端正在服务器端进行缓冲。来自docs :

There is also no guarantee that the data you send will appear on the network immediately. To increase network efficiency, the underlying system may delay transmission until a significant amount of outgoing data is collected. A successful completion of the Send method means that the underlying system has had room to buffer your data for a network send.

因此您需要确保套接字缓冲区被刷新。但是，Socket 上没有 Flush() 方法。 .那么，该怎么办？

1. 最简单的做法是在处理完套接字后立即处理它:

           int byteCount;
           using (var serverSocket = server.AcceptSocket())
           {
               byteCount = serverSocket.Send(bytes);
           }
           Console.WriteLine("server send: " + byteCount);
   

   (用完一次性用品后立即处理是个好主意。)

2. 或者，将 serverSocket 包装在拥有套接字的 NetworkStream 中，然后释放流(这相当于同一件事):

           var serverSocket = server.AcceptSocket();
           using (var ns = new NetworkStream(serverSocket, true))
           {
               ns.Write(bytes, 0, bytes.Length);
           }
   

   (但请参阅 NetworkStream.Write vs. Socket.Send，这表明有时有必要检查从 serverSocket.Send(bytes) 返回的值。)

您可能需要考虑处理 SocketError.NoBufferSpaceAvailable .这里有一个如何做到这一点的建议:C# Examples: Socket Send and Receive [C#] .