[英]Sockets in C#, how can I asynchronously read and write data through a NetworkStream
[我僅限於Visual Studio 2010,因此,C#4。異步和等待對我不可用。]
我正在為我的一個項目開發網絡架構,該項目通過服務器和客戶端之間的網絡發送數據包,但是客戶端和服務器必須在等待時繼續運行,因此代碼必須是非阻塞的,因此我想使用異步方法。 但是,除了簡單的同步一次性IO之外,我對執行的操作知之甚少,尤其是在使用NetworkStream時。 我想做的是:
1)客戶端連接到服務器
2)服務器接受連接
3)服務器等待來自客戶端的數據
4)服務器處理數據
5)服務器響應客戶端
6)打開連接時,請從3開始重復。
我想使用NetworkStream包裝套接字。 但是我是異步I / O的新手,我不確定在等待響應時,特別是在NetworkStream中,如何在不阻止服務器/客戶端代碼其他部分的情況下執行此操作。 在我的研究中,我看到了使用如下形式的示例:
while(true){
socket.BeginAccept(new AsyncCallback(AcceptCallback), socket );
}
但是似乎該循環仍會阻止應用程序。 誰能給我一些關於如何做到這一點的指示(公頃)? 我無法找到許多使連接保持打開狀態的示例,只有客戶端連接->客戶端發送->服務器接收->服務器發送->斷開連接。 我不是要完整的代碼,而只是要求提供一些摘要。
這是對NetworkStream
使用async / await的非常簡單的示例:
SocketServer.cs:
class SocketServer
{
private readonly Socket _listen;
public SocketServer(int port)
{
IPEndPoint listenEndPoint = new IPEndPoint(IPAddress.Loopback, port);
_listen = new Socket(SocketType.Stream, ProtocolType.Tcp);
_listen.Bind(listenEndPoint);
_listen.Listen(1);
_listen.BeginAccept(_Accept, null);
}
public void Stop()
{
_listen.Close();
}
private async void _Accept(IAsyncResult result)
{
try
{
using (Socket client = _listen.EndAccept(result))
using (NetworkStream stream = new NetworkStream(client))
using (StreamReader reader = new StreamReader(stream))
using (StreamWriter writer = new StreamWriter(stream))
{
Console.WriteLine("SERVER: accepted new client");
string text;
while ((text = await reader.ReadLineAsync()) != null)
{
Console.WriteLine("SERVER: received \"" + text + "\"");
writer.WriteLine(text);
writer.Flush();
}
}
Console.WriteLine("SERVER: end-of-stream");
// Don't accept a new client until the previous one is done
_listen.BeginAccept(_Accept, null);
}
catch (ObjectDisposedException)
{
Console.WriteLine("SERVER: server was closed");
}
catch (SocketException e)
{
Console.WriteLine("SERVER: Exception: " + e);
}
}
}
Program.cs中:
class Program
{
private const int _kport = 54321;
static void Main(string[] args)
{
SocketServer server = new SocketServer(_kport);
Socket remote = new Socket(SocketType.Stream, ProtocolType.Tcp);
IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Loopback, _kport);
remote.Connect(remoteEndPoint);
using (NetworkStream stream = new NetworkStream(remote))
using (StreamReader reader = new StreamReader(stream))
using (StreamWriter writer = new StreamWriter(stream))
{
Task receiveTask = _Receive(reader);
string text;
Console.WriteLine("CLIENT: connected. Enter text to send...");
while ((text = Console.ReadLine()) != "")
{
writer.WriteLine(text);
writer.Flush();
}
remote.Shutdown(SocketShutdown.Send);
receiveTask.Wait();
}
server.Stop();
}
private static async Task _Receive(StreamReader reader)
{
string receiveText;
while ((receiveText = await reader.ReadLineAsync()) != null)
{
Console.WriteLine("CLIENT: received \"" + receiveText + "\"");
}
Console.WriteLine("CLIENT: end-of-stream");
}
}
這是一個非常簡單的示例,在同一過程中同時托管服務器和客戶端,並且一次僅接受一個連接。 它實際上只是出於說明目的。 現實世界中的場景無疑將包括其他滿足其需求的功能。
在這里,我將NetworkStream
包裝在StreamReader
和StreamWriter
。 請注意,您必須調用Flush()
以確保實際發送了數據。 為了更好地控制I / O,您當然可以直接使用NetworkStream
。 只需使用Stream.ReadAsync()
方法而不是StreamReader.ReadLineAsync()
。 還要注意,在我的示例中,編寫是同步的。 如果願意,您也可以使用與閱讀所示相同的基本技術來使此異步。
編輯:
OP表示他們無法使用async
/ await
。 這是使用NetworkStream
和舊式Begin/EndXXX()
API的客戶端版本(當然會對服務器進行類似更改):
using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
namespace TestOldSchoolNetworkStream
{
class Program
{
private const int _kport = 54321;
static void Main(string[] args)
{
SocketServer server = new SocketServer(_kport);
Socket remote = new Socket(SocketType.Stream, ProtocolType.Tcp);
IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Loopback, _kport);
remote.Connect(remoteEndPoint);
using (NetworkStream stream = new NetworkStream(remote))
{
// For convenience, These variables are local and captured by the
// anonymous method callback. A less-primitive implementation would
// encapsulate the client state in a separate class, where these objects
// would be kept. The instance of this object would be then passed to the
// completion callback, or the receive method itself would contain the
// completion callback itself.
ManualResetEvent receiveMonitor = new ManualResetEvent(false);
byte[] rgbReceive = new byte[8192];
char[] rgch = new char[Encoding.UTF8.GetMaxCharCount(rgbReceive.Length)];
Decoder decoder = Encoding.UTF8.GetDecoder();
StringBuilder receiveBuffer = new StringBuilder();
stream.BeginRead(rgbReceive, 0, rgbReceive.Length, result =>
{
_Receive(stream, rgbReceive, rgch, decoder, receiveBuffer, receiveMonitor, result);
}, null);
string text;
Console.WriteLine("CLIENT: connected. Enter text to send...");
while ((text = Console.ReadLine()) != "")
{
byte[] rgbSend = Encoding.UTF8.GetBytes(text + Environment.NewLine);
remote.BeginSend(rgbSend, 0, rgbSend.Length, SocketFlags.None, _Send, Tuple.Create(remote, rgbSend.Length));
}
remote.Shutdown(SocketShutdown.Send);
receiveMonitor.WaitOne();
}
server.Stop();
}
private static void _Receive(NetworkStream stream, byte[] rgb, char[] rgch, Decoder decoder, StringBuilder receiveBuffer, EventWaitHandle monitor, IAsyncResult result)
{
try
{
int byteCount = stream.EndRead(result);
string fullLine = null;
if (byteCount > 0)
{
int charCount = decoder.GetChars(rgb, 0, byteCount, rgch, 0);
receiveBuffer.Append(rgch, 0, charCount);
int newLineIndex = IndexOf(receiveBuffer, Environment.NewLine);
if (newLineIndex >= 0)
{
fullLine = receiveBuffer.ToString(0, newLineIndex);
receiveBuffer.Remove(0, newLineIndex + Environment.NewLine.Length);
}
stream.BeginRead(rgb, 0, rgb.Length, result1 =>
{
_Receive(stream, rgb, rgch, decoder, receiveBuffer, monitor, result1);
}, null);
}
else
{
Console.WriteLine("CLIENT: end-of-stream");
fullLine = receiveBuffer.ToString();
monitor.Set();
}
if (!string.IsNullOrEmpty(fullLine))
{
Console.WriteLine("CLIENT: received \"" + fullLine + "\"");
}
}
catch (IOException e)
{
Console.WriteLine("CLIENT: Exception: " + e);
}
}
private static int IndexOf(StringBuilder sb, string text)
{
for (int i = 0; i < sb.Length - text.Length + 1; i++)
{
bool match = true;
for (int j = 0; j < text.Length; j++)
{
if (sb[i + j] != text[j])
{
match = false;
break;
}
}
if (match)
{
return i;
}
}
return -1;
}
private static void _Send(IAsyncResult result)
{
try
{
Tuple<Socket, int> state = (Tuple<Socket, int>)result.AsyncState;
int actualLength = state.Item1.EndSend(result);
if (state.Item2 != actualLength)
{
// Should never happen...the async operation should not complete until
// the full buffer has been successfully sent,
Console.WriteLine("CLIENT: send completed with only partial success");
}
}
catch (IOException e)
{
Console.WriteLine("CLIENT: Exception: " + e);
}
}
}
}
請注意,即使遺漏了一堆異常處理邏輯,該代碼也相當長,至少部分原因是TextReader
沒有內置的異步API,因此對輸入數據的處理是這里更加詳細。 當然,這是針對簡單的基於行的文本交換協議。 就數據拆包方面而言,其他協議可能會或多或少復雜,但是NetworkStream
的底層讀取和寫入元素將是相同的。
這是很好的示例,展示了C#中實現異步通信的一般思想
異步客戶端套接字示例: http : //msdn.microsoft.com/zh-cn/library/bew39x2a(v=vs.110).aspx
異步服務器套接字示例: http : //msdn.microsoft.com/zh-cn/library/fx6588te%28v=vs.110%29.aspx
服務器示例中的代碼綁定到套接字。 並開始接受客戶。 當某些客戶端連接時,提供給BeginAccept的回調將被調用。 在accept回調中,您可以管理客戶端套接字並開始讀取或寫入。 在accept回調結束時,它發出allDone事件信號,並且主循環開始接受新客戶端。
注意:
public static ManualResetEvent allDone = new ManualResetEvent(false);
這有助於避免浪費CPU循環。
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