我正在编写代码，允许Android客户端连接到C＃服务器套接字。客户端和服务器工作正常，但我无法关闭或断开套接字。
服务器由点击事件启动：
private void btnStartServer_Click(object sender, EventArgs e)
{
AsynchronousSocketListener Async = new AsynchronousSocketListener();
receiveThread = new Thread(new ThreadStart(Async.StartListening));
receiveThread.Start();
btnStartServer.Enabled = false;
btnStopServer.Enabled = true;
MessageBox.Show("Server Started");
}
然后是大部分服务器代码：
// 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 void StartListening()
{
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 3000);
System.Diagnostics.Debug.WriteLine(ipAddress);
// 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 );
Singleton s = Singleton.Instance;
if (s.getIsEnded() == false)
{
// Wait until a connection is made before continuing.
allDone.WaitOne();
}
else
{
listener.Shutdown(SocketShutdown.Both);
listener.Disconnect(true);
break;
}
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public static void AcceptCallback(IAsyncResult ar)
{
// 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);
// Signal the main thread to continue.
allDone.Set();
}
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 );
if (content.Equals("end<EOF>"))
{
Console.WriteLine("Should end");
Singleton s = Singleton.Instance;
s.setIsEnded(true);
}
// 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());
}
}
}
使用单例我可以保留一个唯一的变量来检查服务器是否应该运行。这在上面的StartListening()方法中进行了检查：
public class Singleton
{
private static Singleton instance;
private Boolean isEnded = false;
private Singleton() { }
public static Singleton Instance
{
get
{
if (instance == null)
{
instance = new Singleton();
}
return instance;
}
}
public void setIsEnded(Boolean setter)
{
isEnded = setter;
}
public Boolean getIsEnded()
{
return isEnded;
}
}
最后尝试通过向服务器发送带有字符串"end<EOF>"的消息来停止服务器。 ReadCallback()处的服务器逻辑将通知单例设置isEnded = true。这不是一个很好的解决方案，但这是我在撰写本文时能够完成一半工作的唯一方法。断开套接字的逻辑位于StartListening()。理想情况下，它会断开连接，以便可以再次启动套接字。
当我尝试断开然后再次启动套接字时会发生此错误：
A first chance exception of type 'System.Net.Sockets.SocketException' occurred in System.dll
System.Net.Sockets.SocketException (0x80004005): Only one usage of each socket address (protocol/network address/port) is normally permitted
at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Bind(EndPoint localEP)
at StartServer.AsynchronousSocketListener.StartListening() in c:\Users\Conor\Desktop\StartServer\StartServer\StartServer.cs:line 89
如果我停止服务器然后尝试从android客户端发送一个字符串，则在服务器上收到消息，然后我在服务器控制台上收到以下消息：
System.Net.Sockets.SocketException (0x80004005): A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied
at System.Net.Sockets.Socket.Shutdown(SocketShutdown how)
at StartServer.AsynchronousSocketListener.StartListening()
答案 0 :(得分：0)
这是一个完整的服务器测试控制台程序。使用telnet客户端很容易测试：
telnet localhost 3000
请注意，您将无法看到键入的内容，但是当您按 Enter 时，所有行都将被发送到服务器。但是，由于服务器回显数据（当它收到<EOF>字符串时），您将在telnet控制台中看到它作为响应。
主要是你的代码。 我为你添加了许多* Console.WriteLine *，以便更好地理解事件流，异步Socket使用的多线程特性。
请注意while(true)循环中的更改：当服务器收到end<EOF>时，它不仅会将 IsEnded 设置为 true ，还会设置 ManualResetEvent ，以便等待的侦听线程解除阻塞并注意 IsEnded 标志。
另外，要摆脱第二个 SocketException （在 Socket.Shutdown 中），将不会尝试关闭您的侦听套接字。仅关闭您读取和写入的套接字。
还要注意AcceptCallback中的try-catch(ObjectDisposedException)：使用我的代码，你不会偶然发现这个异常，但是当我编写示例时，我用它来抓住关闭侦听套接字的事件。
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
class Program
{
static void Main(string[] args)
{
var asyncSocketListener = new AsynchronousSocketListener();
var listenerThread = new Thread(asyncSocketListener.StartListening);
listenerThread.Start();
Console.WriteLine("Server Started");
listenerThread.Join();
Console.WriteLine("Press any key to exit...");
Console.ReadKey();
}
public class Singleton
{
private static Singleton instance;
private bool isEnded;
private Singleton() { }
public static Singleton Instance
{
get
{
if (instance == null)
{
instance = new Singleton();
}
return instance;
}
}
public bool IsEnded
{
get { return isEnded; }
set { isEnded = value; }
}
}
public class AsynchronousSocketListener
{
// State object for reading client data asynchronously
private class StateObject
{
// Size of receive buffer.
public const int BufferSize = 1024;
// Receive buffer.
public byte[] Buffer = new byte[BufferSize];
// Client socket.
public Socket WorkSocket;
// Received data string.
public StringBuilder Sb = new StringBuilder();
}
// Thread signal.
private static ManualResetEvent allDone = new ManualResetEvent(false);
public void StartListening()
{
var localEndPoint = new IPEndPoint(IPAddress.Any, 3000);
var 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);
Console.WriteLine("Listening on {0}...", localEndPoint.ToString());
while (true)
{
allDone.Reset();
if (Singleton.Instance.IsEnded)
{
Console.WriteLine("Closing listener socket...");
listener.Close();
break;
}
Console.WriteLine("Waiting for a new connection...");
listener.BeginAccept(AcceptCallback, state: listener);
allDone.WaitOne();
}
Console.WriteLine("Server stopped.");
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public static void AcceptCallback(IAsyncResult ar)
{
Socket clientSocket;
try
{
clientSocket = ((Socket)ar.AsyncState).EndAccept(ar);
}
catch (ObjectDisposedException)
{
Console.WriteLine(" Listening socket has been closed.");
allDone.Set();
return;
}
Console.WriteLine(" Connection accepted {0}", clientSocket.RemoteEndPoint.ToString());
var stateObject = new StateObject { WorkSocket = clientSocket };
clientSocket.BeginReceive(stateObject.Buffer, 0, StateObject.BufferSize, 0, ReadCallback, stateObject);
// Signal the main thread to continue.
Console.WriteLine(" Signal the main thread to accept a new connection");
allDone.Set();
}
public static void ReadCallback(IAsyncResult ar)
{
string content;
// Retrieve the state object and the handler socket
// from the asynchronous state object.
var stateObject = (StateObject)ar.AsyncState;
Socket clientSocket = stateObject.WorkSocket;
// Read data from the client socket.
int bytesRead = clientSocket.EndReceive(ar);
if (bytesRead > 0)
{
// There might be more data, so store the data received so far.
stateObject.Sb.Append(Encoding.ASCII.GetString(stateObject.Buffer, 0, bytesRead));
// Check for end-of-file tag. If it is not there, read
// more data.
content = stateObject.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);
if (content.Equals("end<EOF>"))
{
Console.WriteLine(" !!!Should stop the server");
Singleton.Instance.IsEnded = true;
allDone.Set();
}
// Echo the data back to the client.
byte[] byteData = Encoding.ASCII.GetBytes(content);
clientSocket.BeginSend(byteData, 0, byteData.Length, 0, WriteCallback, clientSocket);
}
else
{
// Not all data received. Get more.
clientSocket.BeginReceive(stateObject.Buffer, 0, StateObject.BufferSize, 0, ReadCallback, stateObject);
}
}
}
private static void WriteCallback(IAsyncResult ar)
{
try
{
// Retrieve the socket from the state object.
var clientSocket = (Socket)ar.AsyncState;
// Complete sending the data to the remote device.
int bytesSent = clientSocket.EndSend(ar);
Console.WriteLine(" Sent {0} bytes to client.", bytesSent);
Console.WriteLine(" Disconnecting the client...");
clientSocket.Shutdown(SocketShutdown.Both);
clientSocket.Close();
Console.WriteLine(" Client disconnected.");
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
}
}