我有两个简单的应用程序：
在特定 tcp 端口上等待客户端连接的服务器应用程序。然后听他说什么，发回一些反馈并断开该客户。
一个表单应用程序，它连接到服务器应用程序，然后说点什么，然后等待反馈并断开与服务器的连接，然后在表单中显示反馈。
尽管服务器应用程序似乎表现正确（我已经使用 Telnet 对其进行了测试，并且我看到了反馈，并且我看到在反馈之后直接发生了断开连接），但是表单应用程序似乎没有注意到与服务器的断开连接。（即使在服务器断开连接后，TcpClient.Connected 似乎仍然存在）
我的问题是：为什么 TcpClient.Connected 保持真实，我如何知道服务器是否/何时断开连接？
这是我的完整代码：
表格申请：
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Windows.Forms;
using System.Threading;
namespace Sender
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void sendButton_Click(object sender, EventArgs e)
{
TcpClient tcpClient = new TcpClient();
tcpClient.Connect(IPAddress.Parse("127.0.0.1"), 81);
responseLabel.Text = "waiting for response...";
responseLabel.Invalidate();
// write request
NetworkStream networkStream = tcpClient.GetStream();
byte[] buffer = (new ASCIIEncoding()).GetBytes("Hello World! ");
networkStream.Write(buffer, 0, buffer.Length);
networkStream.Flush();
// read response
Thread readThread = new Thread(new ParameterizedThreadStart(ReadResponse));
readThread.Start(tcpClient);
}
void ReadResponse(object arg)
{
TcpClient tcpClient = (TcpClient)arg;
StringBuilder stringBuilder = new StringBuilder();
NetworkStream networkStream = tcpClient.GetStream();
bool timeout = false;
DateTime lastActivity = DateTime.Now;
while (tcpClient.Connected && !timeout)
{
if (networkStream.DataAvailable)
{
lastActivity = DateTime.Now;
while (networkStream.DataAvailable)
{
byte[] incomingBuffer = new byte[1024];
networkStream.Read(incomingBuffer, 0, 1024);
char[] receivedChars = new char[1024];
(new ASCIIEncoding()).GetDecoder().GetChars(incomingBuffer, 0, 1024, receivedChars, 0);
stringBuilder.Append(receivedChars);
}
}
else
{
if (DateTime.Now > lastActivity.AddSeconds(60))
timeout = true;
}
System.Threading.Thread.Sleep(50);
}
Invoke((MethodInvoker)delegate
{
responseLabel.Text = "Response from Listener:\n" + stringBuilder.ToString();
responseLabel.Invalidate();
});
if (timeout)
{
Console.Write("A timeout occured\n");
networkStream.Close();
tcpClient.Close();
}
}
}
}
服务器应用：
using System.Net;
using System.Net.Sockets;
using System.Text;
using System;
using System.Threading;
namespace Listener
{
class Program
{
static void Main(string[] args)
{
var tcpListener = new TcpListener(IPAddress.Any, 81);
tcpListener.Start();
Thread clientThread = new Thread(new ParameterizedThreadStart(Listen));
clientThread.Start(tcpListener);
}
static void Listen(object arg)
{
TcpListener tcpListener = (TcpListener)arg;
while (true)
{
TcpClient tcpClient = tcpListener.AcceptTcpClient();
Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClient));
clientThread.Start(tcpClient);
}
}
static void HandleClient(object arg)
{
TcpClient tcpClient = (TcpClient)arg;
StringBuilder stringBuilder = new StringBuilder();
ASCIIEncoding encoder = new ASCIIEncoding();
DateTime lastActivity = DateTime.Now;
// read request
NetworkStream networkStream = tcpClient.GetStream();
int timeout = 5; // gives client some time to send data after connecting
while (DateTime.Now < lastActivity.AddSeconds(timeout) && stringBuilder.Length==0)
{
if (!networkStream.DataAvailable)
{
System.Threading.Thread.Sleep(50);
}
else
{
while (networkStream.DataAvailable)
{
lastActivity = DateTime.Now;
byte[] incomingBuffer = new byte[1024];
networkStream.Read(incomingBuffer, 0, 1024);
char[] receivedChars = new char[1024];
encoder.GetDecoder().GetChars(incomingBuffer, 0, 1024, receivedChars, 0);
stringBuilder.Append(receivedChars);
}
}
}
string request = stringBuilder.ToString();
// write response
string response = "The listener just received: " + request;
byte[] outgoingBuffer = encoder.GetBytes(response);
networkStream.Write(outgoingBuffer, 0, outgoingBuffer.Length);
networkStream.Flush();
networkStream.Close();
tcpClient.Close();
}
}
}