如何在单独的线程中正确关闭异步套接字侦听器

Question

我使用C#类连接不同的子窗体。项目为MDI类型。在连接形式中，有一个由线程调用的异步套接字列表器。当我关闭应用程序时，我无法关闭侦听器，程序仍处于任务管理器中。问题与打开的侦听器有关。在形式连接中放入此代码：

private AsynchronousSocketListener socketListener;          // Per socket in ascolto da parte delle App to Machine
private Thread t_listener;
public c_masterConn() //Costructor
{
socketListener = new AsynchronousSocketListener();          // Socketlistner async
t_listener = new Thread(socketListener.StartListening);     // Thread for socketlistener
t_listener.Start();                                         // Start socketlistener
}
public void StopThr() //Stop listner thread
{
t_listener.Interrupt();
}
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.
// 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 void StopListening() // Stop Listening
{
allDone.Close();
}
}

在形式的孩子，我把这个：

private void hideMonBt_Click(object sender, EventArgs e)
{
this.Hide();
m_engMonitor.m_masterConn.StopThr(); // Stop "server"
}
private void c_frmMonitor_Load(object sender, EventArgs e)
{
m_engMonitor.socketConnect(); // Start "server" connection
}

我不确定在连接形式中使用此代码：

public void StopListening() // Stop Listening
{
allDone.Close();
}
public void StopThr() //Stop listner thread
{
t_listener.Interrupt();
}

我做错了什么？谢谢

Answer 1

问题是你永远不会停止倾听。你在一个无休止的循环中运行你的套接字，当你想结束它时，你不是在关闭套接字，而是在中断线程。这相当于把你的门敲下来，而不是打开然后关上。

为了正确地停止收听，请关闭插座。当这种情况发生时，BeginAccept将抛出一个ObjectDisposedException。根本没有必要中断你的线程：

public class AsynchronousSocketListener : IDisposable
{
Socket listener;
// Thread signal.
public 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.
// 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.
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 (ObjectDisposedException)
{
//Console.WriteLine("Listener closed.");
}
catch (Exception e)
{
//Console.WriteLine(e.ToString());
}
//Console.WriteLine("nPress ENTER to continue...");
//Console.Read();
}
//...
public void StopListening() // Stop Listening
{
Socket exListener = Interlocked.Exchange(ref listener, null);
if (exListener != null)
{
exListener.Close();
}
}
public void Dispose()
{
StopListening();
}
}

当您想要结束侦听器时，只需调用StopListening即可。当StartListening退出时，线程将正常结束。

我对你的代码做了一些其他更改：

• 我做了一次性AsynchronousSocketListener。您正在包装一个套接字，并且需要确保在处理侦听器时释放它
• 将allDone从static更改为实例。如果您有多个侦听器(例如，到不同的端口)，它们会共享事件，这是一个错误

您仍然需要做的是：如果在StartListening分配listener的值之前调用StopListening，则侦听不会停止。侦听器将正常启动。这是代码中的一个竞争条件，您必须消除它。

Answer 2

我在这种模式下解决了问题：

class c_masterConn 
{
private AsynchronousSocketListener socketListener;              // socketlistner
private Thread t_listener;
public c_masterConn()                                           //Costructor
{
socketListener = new AsynchronousSocketListener();          // Socketlistner async
t_listener = new Thread(socketListener.StartListening);     // Thread for socketlistener 
t_listener.Start();                                         //  Start socketlistener
}
public void StopConnection()
{
socketListener.StopListening();
}
// 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 
{
Socket listener;
// Thread signal.
public  ManualResetEvent allDone = new ManualResetEvent(false);
public AsynchronousSocketListener()
{
}
public void AcceptCallback(IAsyncResult ar)
{
try
{ // 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);
}
catch (Exception ex)
{ }
}
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 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.
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 (ObjectDisposedException)
{
//Console.WriteLine("Listener closed.");
}
catch (Exception e)
{
//Console.WriteLine(e.ToString());
}
//Console.WriteLine("nPress ENTER to continue...");
//Console.Read();
}
//...
public void StopListening() // Stop Listening
{
Socket exListener = Interlocked.Exchange(ref listener, null);
if (exListener != null)
{
exListener.Close();
}
}
}

我使用Sefe的解决方案，但在调用函数"dispose"时会进行修改。我在父窗体的事件"Form_close"中调用StopListening函数。在此模式下，应用程序将正确关闭。