我最近一直在将 SocketAsyncEventArgs 用于一个项目，并且遇到了一些问题，即 ReceiveAsync 偶尔会以与通过 SendAsync 发送的顺序不同的顺序获取数据。在 SendAsync 方法中发送的每个数据块都会被维护，但这些块的顺序不一定正确。也许我对 SendAsync 方法的理解不正确，但我认为特别是使用 SocketType.Stream 和 ProtocolType.Tcp 可以确保保持顺序。我知道底层进程将不可避免地破坏消息，并且 ReceiveAsync 通常会读取少于缓冲区分配的内容。但我假设发送和接收流会保持秩序。
我开发了一个显示问题的测试控制台程序。它每次尝试使用一组不同的套接字和端口运行大约 20 次。在我的笔记本电脑上，它通常会通过一次然后第二次失败；通常在期待第二个块时会收到一个稍后的块。从其他测试中，我知道预期的块最终确实会出现，只是不按顺序出现。
需要注意的是，我能够在 Windows 2008 远程服务器上对其进行测试并且没有任何问题。但是，它从未接近在我的笔记本电脑上完成。事实上，如果我让调试执行在异常中断中挂起一段时间，我已经让它不止一次地完全冻结了我的笔记本电脑，并且不得不进行硬重启。这是我在 Windows 7 上使用 VS2017 运行的工作笔记本电脑。我不确定这是否是一个因素，但它正在运行 Symantec Endpoint Protection，尽管我在日志中没有发现任何内容。
所以我的问题是，我对 SocketAsyncEventArgs 的运作方式有错误的看法吗？还是我的代码是一场灾难（也许两者兼而有之）？它是我的笔记本电脑独有的吗？（最后一个让我觉得我正在为编程新手做准备，并且您认为编译器一定有问题。）
using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Threading.Tasks;
static class DumTest
{
static void Main(string[] args)
{
for (int i = 9177; i < 9199; i++)
{
RunDum(i);
//Thread.Sleep(350);
}
Console.WriteLine("all done.");
Console.ReadLine();
}
static void RunDum(int port)
{
var dr = new DumReceiver(port);
var ds = new DumSender(port);
dr.Acception.Wait();
ds.Connection.Wait();
dr.Completion.Wait();
ds.Completion.Wait();
Console.WriteLine($"Completed {port}. " +
$"sent: {ds.SegmentsSent} segments, received: {dr.SegmentsRead} segments");
}
}
class DumReceiver
{
private readonly SocketAsyncEventArgs eva = new SocketAsyncEventArgs();
private readonly TaskCompletionSource<object> tcsAcc = new TaskCompletionSource<object>();
private TaskCompletionSource<object> tcsRcv;
private Socket socket;
internal DumReceiver(int port)
{
this.eva.Completed += this.Received;
var lstSock = new Socket(
AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
var localIP = Dns.GetHostEntry(Dns.GetHostName()).AddressList
.First(i => i.AddressFamily == AddressFamily.InterNetwork);
lstSock.Bind(new IPEndPoint(localIP, port));
lstSock.Listen(1);
var saea = new SocketAsyncEventArgs();
saea.Completed += this.AcceptCompleted;
lstSock.AcceptAsync(saea);
}
internal Task Acception => this.tcsAcc.Task;
internal Task Completion { get; private set; }
internal int SegmentsRead { get; private set; }
private void AcceptCompleted(object sender, SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
this.socket = e.AcceptSocket;
e.Dispose();
try
{
this.Completion = this.ReceiveLupeAsync();
}
finally
{
this.tcsAcc.SetResult(null);
}
}
else
{
this.tcsAcc.SetException(new SocketException((int)e.SocketError));
}
}
private async Task ReceiveLupeAsync()
{
var buf = new byte[8196];
byte bufSeg = 1;
int pos = 0;
while (true)
{
this.tcsRcv = new TaskCompletionSource<object>();
this.eva.SetBuffer(buf, pos, 8196 - pos);
if (this.socket.ReceiveAsync(this.eva))
{
await this.tcsRcv.Task.ConfigureAwait(false);
}
if (this.eva.SocketError != SocketError.Success)
{
throw new SocketException((int)eva.SocketError);
}
if (this.eva.BytesTransferred == 0)
{
if (pos != 0)
{
throw new EndOfStreamException();
}
break;
}
pos += this.eva.BytesTransferred;
if (pos == 8196)
{
pos = 0;
for (int i = 0; i < 8196; i++)
{
if (buf[i] != bufSeg)
{
var msg = $"Expected {bufSeg} but read {buf[i]} ({i} of 8196). " +
$"Last read: {this.eva.BytesTransferred}.";
Console.WriteLine(msg);
throw new Exception(msg);
}
}
this.SegmentsRead++;
bufSeg = (byte)(this.SegmentsRead + 1);
}
}
}
private void Received(object s, SocketAsyncEventArgs e) => this.tcsRcv.SetResult(null);
}
class DumSender
{
private readonly SocketAsyncEventArgs eva = new SocketAsyncEventArgs();
private readonly Socket socket = new Socket(
AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
private readonly TaskCompletionSource<object> tcsCon = new TaskCompletionSource<object>();
private TaskCompletionSource<object> tcsSnd;
internal DumSender(int port)
{
this.eva.Completed += this.Sent;
var saea = new SocketAsyncEventArgs();
var localIP = Dns.GetHostEntry(Dns.GetHostName()).AddressList
.First(i => i.AddressFamily == AddressFamily.InterNetwork);
saea.RemoteEndPoint = new IPEndPoint(localIP, port);
saea.Completed += this.ConnectionCompleted;
this.socket.ConnectAsync(saea);
}
internal Task Connection => this.tcsCon.Task;
internal Task Completion { get; private set; }
internal int SegmentsSent { get; private set; }
private void ConnectionCompleted(object sender, SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
e.Dispose();
try
{
this.Completion = this.SendLupeAsync();
}
finally
{
this.tcsCon.SetResult(null);
}
}
else
{
this.tcsCon.SetException(new SocketException((int)e.SocketError));
}
}
private async Task SendLupeAsync()
{
var buf = new byte[8196];
byte bufSeg = 1;
while (true)
{
for (int i = 0; i < 8196; i++)
{
buf[i] = bufSeg;
}
this.tcsSnd = new TaskCompletionSource<object>();
this.eva.SetBuffer(buf, 0, 8196);
if (this.socket.SendAsync(this.eva))
{
await this.tcsSnd.Task.ConfigureAwait(false);
}
if (this.eva.SocketError != SocketError.Success)
{
throw new SocketException((int)this.eva.SocketError);
}
if (this.eva.BytesTransferred != 8196)
{
throw new SocketException();
}
if (++this.SegmentsSent == 299)
{
break;
}
bufSeg = (byte)(this.SegmentsSent + 1);
}
this.socket.Shutdown(SocketShutdown.Both);
}
private void Sent(object s, SocketAsyncEventArgs e) => this.tcsSnd.SetResult(null);
}