一个最简单的服务端和客户端(用CSocket)

功能：服务器端程序处于监听状态，等待客户端连接。客户端发来数据后，服务端回发一个消息，同时关闭连接！

源码下载

服务器(采用一个监听线程)核心代码：

BOOL CListenThread::InitInstance()
{
// 	if (!AfxSocketInit())
// 	{
// 		AfxMessageBox(IDP_SOCKETS_INIT_FAILED);
// 		return FALSE;
// 	}
	m_bListening = TRUE;			// 线程启动时默认处于监听状态
	while(1)
	{
		if(m_bListening)
		{
			StartListen();
		}
	}

	return TRUE;
}

int CListenThread::ExitInstance()
{
	StopListen();

	return CWinThread::ExitInstance();
}

BOOL CListenThread::StartListen()
{
	CString sResult;
	try
	{
		if(m_pListenSocket == NULL)
			m_pListenSocket = new CSocket;
		if(m_pListenSocket && m_pListenSocket->Create(m_nPort))		// Create()内部包含了Bind()
		{
			m_pListenSocket->Listen();
			m_pMainDlg->ShowInfo("启动监听成功");
			PostMessage(m_pMainDlg->GetSafeHwnd(), WM_ENABLE_LISTENING, 0, 0);
			while(1)
			{
				CSocket clientSocket;
				if(m_pListenSocket->Accept(clientSocket))
				{
					char buffer[1024] = {0};
					CString sText;
					clientSocket.Receive(buffer, 1024);
					sText = buffer;
					m_pMainDlg->ShowInfo(sText);

					CString s = "Thank you, JoeBlack";
					clientSocket.Send(s, s.GetLength());
//					send(clientSocket.m_hSocket, s, s.GetLength(), 0);		// 与上一句等效

					if(sText == "close")			// stop listening
					{
						StopListen();
						break;
					}
					else if(sText == "quit")		// post a message to let the main thread delete listen-thread
					{
						EndMyThread();
						return TRUE;
					}
				}
			}
			return TRUE;
		}
	}
	catch (CException* e)
	{
		char str[300] = {0};
		e->GetErrorMessage(str, 300);
		sResult.Format("启动监听失败，错误码：%d", str);
		m_pMainDlg->ShowInfo(sResult);
	}
	catch(...)
	{
		int err;
		err = WSAGetLastError();
		sResult.Format("启动监听失败，错误码：%d", err);
		m_pMainDlg->ShowInfo(sResult);
	}
	m_bListening = FALSE;

	return FALSE;
}

BOOL CListenThread::StopListen()					// 停止服务器监听
{
	if(m_pListenSocket)
	{
		m_pListenSocket->Close();
		delete m_pListenSocket;
		m_pListenSocket = NULL;
		m_pMainDlg->ShowInfo("Stop listening successful");
		m_bListening = FALSE;
		m_pMainDlg->PostMessage(WM_ENABLE_LISTENING, 1, 0);	// 让“启动监听”按钮变为可用
	}
	return TRUE;
}

BOOL CListenThread::EndMyThread()						// 关闭CSocket并退出本线程
{
	StopListen();
	m_pMainDlg->ShowInfo("Exit from Listen-Thread");
	PostMessage(m_pMainDlg->GetSafeHwnd(), WM_FREE_LISTENTHREAD, 0, 0);

	return TRUE;
}

服务端程序实现监听，当收到close或quit时，会停止监听，这时客户端即使发来数据，也不会被收到。服务器端点击窗口中的“开启监听”后，可以重新开启监听线程。

客户端程序(向server发送消息并接收返回值)：

void CClientAppDlg::OnBtnSend()
{
	CSocket sendSocket;
	if(sendSocket.Create())
	{
		if(sendSocket.Connect("127.0.0.1", 5050))
		{
			UpdateData();
			sendSocket.Send(m_strEdit, m_strEdit.GetLength());
			Sleep(100);  // 等待服务器端数据返回

			char buf[1024] = {0};
			CString sResponse;
			while(sendSocket.Receive(buf, 1024))
			//while(recv(sendSocket, buf, 1024, 0))
			{
				sResponse += buf;
			}

			MessageBox(sResponse);
			sendSocket.Close();
		}
	}
}