C# 套接字编程多客户端一台服务器
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Socket Programming multiple client one server
提问by Prerak Pradhan
I am just starting out Socket Programming in C# and am now a bit stuck with this problem. How do you handle multiple clients on a single server without creating a thread for each client?
我刚刚开始用 C# 进行套接字编程，现在有点被这个问题困住了。如何在不为每个客户端创建线程的情况下处理单个服务器上的多个客户端？
The one thread for each client works fine when there are say 10 clients but if the client number goes up to a 1000 clients is creating a thread for every single one of them advisable? If there is any other method to do this can someone please tel me?
当有 10 个客户端时，每个客户端的一个线程工作正常，但是如果客户端数量增加到 1000 个客户端，是否建议为每个客户端创建一个线程？如果有任何其他方法可以做到这一点，有人可以给我打电话吗？
采纳答案by Dave Miles
Try to use asynchronous server. The following example program creates a server that receives connection requests from clients. The server is built with an asynchronous socket, so execution of the server application is not suspended while it waits for a connection from a client. The application receives a string from the client, displays the string on the console, and then echoes the string back to the client. The string from the client must contain the string "" to signal the end of the message.
尝试使用异步服务器。以下示例程序创建一个服务器，用于接收来自客户端的连接请求。服务器使用异步套接字构建，因此在等待来自客户端的连接时，服务器应用程序的执行不会暂停。应用程序从客户端接收一个字符串，在控制台上显示该字符串，然后将该字符串回显给客户端。来自客户端的字符串必须包含字符串 "" 以表示消息结束。
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
// State object for reading client data asynchronously
public class StateObject {
// Client socket.
public Socket workSocket = null;
// Size of receive buffer.
public const int BufferSize = 1024;
// Receive buffer.
public byte[] buffer = new byte[BufferSize];
// Received data string.
public StringBuilder sb = new StringBuilder();
}
public class AsynchronousSocketListener {
// Thread signal.
public static ManualResetEvent allDone = new ManualResetEvent(false);
public AsynchronousSocketListener() {
}
public static void StartListening() {
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// The DNS name of the computer
// running the listener is "host.contoso.com".
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp );
// Bind the socket to the local endpoint and listen for incoming connections.
try {
listener.Bind(localEndPoint);
listener.Listen(100);
while (true) {
// Set the event to nonsignaled state.
allDone.Reset();
// Start an asynchronous socket to listen for connections.
Console.WriteLine("Waiting for a connection...");
listener.BeginAccept(
new AsyncCallback(AcceptCallback),
listener );
// Wait until a connection is made before continuing.
allDone.WaitOne();
}
} catch (Exception e) {
Console.WriteLine(e.ToString());
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
public static void AcceptCallback(IAsyncResult ar) {
// Signal the main thread to continue.
allDone.Set();
// Get the socket that handles the client request.
Socket listener = (Socket) ar.AsyncState;
Socket handler = listener.EndAccept(ar);
// Create the state object.
StateObject state = new StateObject();
state.workSocket = handler;
handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(ReadCallback), state);
}
public static void ReadCallback(IAsyncResult ar) {
String content = String.Empty;
// Retrieve the state object and the handler socket
// from the asynchronous state object.
StateObject state = (StateObject) ar.AsyncState;
Socket handler = state.workSocket;
// Read data from the client socket.
int bytesRead = handler.EndReceive(ar);
if (bytesRead > 0) {
// There might be more data, so store the data received so far.
state.sb.Append(Encoding.ASCII.GetString(
state.buffer,0,bytesRead));
// Check for end-of-file tag. If it is not there, read
// more data.
content = state.sb.ToString();
if (content.IndexOf("<EOF>") > -1) {
// All the data has been read from the
// client. Display it on the console.
Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
content.Length, content );
// Echo the data back to the client.
Send(handler, content);
} else {
// Not all data received. Get more.
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(ReadCallback), state);
}
}
}
private static void Send(Socket handler, String data) {
// Convert the string data to byte data using ASCII encoding.
byte[] byteData = Encoding.ASCII.GetBytes(data);
// Begin sending the data to the remote device.
handler.BeginSend(byteData, 0, byteData.Length, 0,
new AsyncCallback(SendCallback), handler);
}
private static void SendCallback(IAsyncResult ar) {
try {
// Retrieve the socket from the state object.
Socket handler = (Socket) ar.AsyncState;
// Complete sending the data to the remote device.
int bytesSent = handler.EndSend(ar);
Console.WriteLine("Sent {0} bytes to client.", bytesSent);
handler.Shutdown(SocketShutdown.Both);
handler.Close();
} catch (Exception e) {
Console.WriteLine(e.ToString());
}
}
public static int Main(String[] args) {
StartListening();
return 0;
}
}
That's will be the best solution.
这将是最好的解决方案。
回答by dutt
Threads can work fine but rarely scales well to that many clients. There are two easy ways and lots of more complex ways to handle that, here's some pseudocode for how the easier two are usually structured to give you an overview.
线程可以正常工作，但很少能很好地扩展到那么多客户端。有两种简单的方法和许多更复杂的方法来处理它，这里有一些伪代码，用于说明通常如何构建更简单的两种方法，以便为您提供概述。
select()
选择（）
This is a call to check which sockets have new clients or data waiting on them, a typical program looks something like this.
这是一个检查哪些套接字有新客户端或数据在等待它们的调用，一个典型的程序看起来像这样。
server = socket(), bind(), listen()
while(run)
status = select(server)
if has new client
newclient = server.accept()
handle add client
if has new data
read and handle data
Which means no threads are needed to handle multiple clients, but it doesn't really scale well either if handle data take a long time, then you won't read new data or accept new clients until that's done.
这意味着不需要线程来处理多个客户端，但是如果处理数据需要很长时间，它也不能很好地扩展，那么在完成之前你不会读取新数据或接受新客户端。
Async sockets
异步套接字
This is another way of handling sockets which is kind of abstracted above select. You just set up callbacks for common events and let the framework do the not-so-heavy lifting.
这是另一种处理套接字的方法，它在 select 之上是一种抽象。您只需为常见事件设置回调，让框架完成不那么繁重的工作。
function handleNewClient() { do stuff and then beginReceive(handleNewData) }
function handleNewData() { do stuff and then beginReceive(handleNewData) }
server = create, bind, listen etc
server.beginAddNewClientHandler(handleNewClient)
server.start()
I think this should scale better if your data handling take a long time. What kind of data handling will you be doing?
如果您的数据处理需要很长时间，我认为这应该可以更好地扩展。您将进行什么样的数据处理？
回答by Kaveh Shahbazian
Thiscould be a good starting point. If you want to avoid 1 thread <-> 1 client; then you should use async socket facilities provided in .NET. Core object to use here is SocketAsyncEventArgs.
这可能是一个很好的起点。如果你想避免 1 个线程 <-> 1 个客户端；那么您应该使用 .NET 中提供的异步套接字设施。这里使用的核心对象是SocketAsyncEventArgs。
