Simple MFC UDP example

 // SimpleUDPDlg.cpp : implementation file  
 //  
 #include "stdafx.h"  
 #include "SimpleUDP.h"  
 #include "SimpleUDPDlg.h"  
 #include "afxsock.h"  
 #include "ClientSend.h"  
 #ifdef _DEBUG  
 #define new DEBUG_NEW  
 #undef THIS_FILE  
 static char THIS_FILE[] = __FILE__;  
 #endif  
 #define ECHOMAX 1024  
 /////////////////////////////////////////////////////////////////////////////  
 // CAboutDlg dialog used for App About  
      HANDLE thr;  
      unsigned long id1;  
 class CAboutDlg : public CDialog  
 {  
 public:  
      CAboutDlg();  
 // Dialog Data  
      //{{AFX_DATA(CAboutDlg)  
      enum { IDD = IDD_ABOUTBOX };  
      //}}AFX_DATA  
      // ClassWizard generated virtual function overrides  
      //{{AFX_VIRTUAL(CAboutDlg)  
      protected:  
      virtual void DoDataExchange(CDataExchange* pDX);  // DDX/DDV support  
      //}}AFX_VIRTUAL  
 // Implementation  
 protected:  
      //{{AFX_MSG(CAboutDlg)  
      //}}AFX_MSG  
      DECLARE_MESSAGE_MAP()  
 };  
 CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)  
 {  
      //{{AFX_DATA_INIT(CAboutDlg)  
      //}}AFX_DATA_INIT  
 }  
 void CAboutDlg::DoDataExchange(CDataExchange* pDX)  
 {  
      CDialog::DoDataExchange(pDX);  
      //{{AFX_DATA_MAP(CAboutDlg)  
      //}}AFX_DATA_MAP  
 }  
 BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)  
      //{{AFX_MSG_MAP(CAboutDlg)  
           // No message handlers  
      //}}AFX_MSG_MAP  
 END_MESSAGE_MAP()  
 /////////////////////////////////////////////////////////////////////////////  
 // CSimpleUDPDlg dialog  
 CSimpleUDPDlg::CSimpleUDPDlg(CWnd* pParent /*=NULL*/)  
      : CDialog(CSimpleUDPDlg::IDD, pParent)  
 {  
      //{{AFX_DATA_INIT(CSimpleUDPDlg)  
           // NOTE: the ClassWizard will add member initialization here  
      //}}AFX_DATA_INIT  
      // Note that LoadIcon does not require a subsequent DestroyIcon in Win32  
      m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);  
 }  
 void CSimpleUDPDlg::DoDataExchange(CDataExchange* pDX)  
 {  
      CDialog::DoDataExchange(pDX);  
      //{{AFX_DATA_MAP(CSimpleUDPDlg)  
      DDX_Control(pDX, IDC_EDIT1, m_edit);  
      //}}AFX_DATA_MAP  
 }  
 BEGIN_MESSAGE_MAP(CSimpleUDPDlg, CDialog)  
      //{{AFX_MSG_MAP(CSimpleUDPDlg)  
      ON_WM_SYSCOMMAND()  
      ON_WM_PAINT()  
      ON_WM_QUERYDRAGICON()  
      ON_BN_CLICKED(IDC_BUTTON1, OnStart)  
      //}}AFX_MSG_MAP  
 END_MESSAGE_MAP()  
 /////////////////////////////////////////////////////////////////////////////  
 // CSimpleUDPDlg message handlers  
 UINT ReceiveData(LPVOID pParam)  
 {  
      CSimpleUDPDlg *dlg=(CSimpleUDPDlg*)pParam;  
      AfxSocketInit(NULL);  
      CSocket echoServer;   
       // Create socket for sending/receiving datagrams  
       if (echoServer.Create(514, SOCK_DGRAM, NULL)== 0) {  
           AfxMessageBox("Create() failed");  
       }  
      for(;;) { // Run forever  
   // Client address  
   SOCKADDR_IN echoClntAddr;   
   // Set the size of the in-out parameter  
   int clntAddrLen = sizeof(echoClntAddr);  
   // Buffer for echo string  
   char echoBuffer[ECHOMAX];   
   // Block until receive message from a client  
   int recvMsgSize = echoServer.ReceiveFrom(echoBuffer,   
       ECHOMAX, (SOCKADDR*)&echoClntAddr, &clntAddrLen, 0);  
   if (recvMsgSize < 0) {  
    AfxMessageBox("RecvFrom() failed");  
   }  
      echoBuffer[recvMsgSize]='\0';  
   dlg->m_edit.ReplaceSel(echoBuffer);  
      dlg->m_edit.ReplaceSel("\r\n");  
  }  
 }  
 BOOL CSimpleUDPDlg::OnInitDialog()  
 {  
      CDialog::OnInitDialog();  
      // Add "About..." menu item to system menu.  
      // IDM_ABOUTBOX must be in the system command range.  
      ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);  
      ASSERT(IDM_ABOUTBOX < 0xF000);  
      CMenu* pSysMenu = GetSystemMenu(FALSE);  
      if (pSysMenu != NULL)  
      {  
           CString strAboutMenu;  
           strAboutMenu.LoadString(IDS_ABOUTBOX);  
           if (!strAboutMenu.IsEmpty())  
           {  
                pSysMenu->AppendMenu(MF_SEPARATOR);  
                pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);  
           }  
      }  
      // Set the icon for this dialog. The framework does this automatically  
      // when the application's main window is not a dialog  
      SetIcon(m_hIcon, TRUE);               // Set big icon  
      SetIcon(m_hIcon, FALSE);          // Set small icon  
      thr=CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)ReceiveData,this,NULL,&id1);  
      // TODO: Add extra initialization here  
      return TRUE; // return TRUE unless you set the focus to a control  
 }  
 void CSimpleUDPDlg::OnSysCommand(UINT nID, LPARAM lParam)  
 {  
      if ((nID & 0xFFF0) == IDM_ABOUTBOX)  
      {  
           CAboutDlg dlgAbout;  
           dlgAbout.DoModal();  
      }  
      else  
      {  
           CDialog::OnSysCommand(nID, lParam);  
      }  
 }  
 // If you add a minimize button to your dialog, you will need the code below  
 // to draw the icon. For MFC applications using the document/view model,  
 // this is automatically done for you by the framework.  
 void CSimpleUDPDlg::OnPaint()   
 {  
      if (IsIconic())  
      {  
           CPaintDC dc(this); // device context for painting  
           SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);  
           // Center icon in client rectangle  
           int cxIcon = GetSystemMetrics(SM_CXICON);  
           int cyIcon = GetSystemMetrics(SM_CYICON);  
           CRect rect;  
           GetClientRect(&rect);  
           int x = (rect.Width() - cxIcon + 1) / 2;  
           int y = (rect.Height() - cyIcon + 1) / 2;  
           // Draw the icon  
           dc.DrawIcon(x, y, m_hIcon);  
      }  
      else  
      {  
           CDialog::OnPaint();  
      }  
 }  
 // The system calls this to obtain the cursor to display while the user drags  
 // the minimized window.  
 HCURSOR CSimpleUDPDlg::OnQueryDragIcon()  
 {  
      return (HCURSOR) m_hIcon;  
 }  
 void CSimpleUDPDlg::OnStart()   
 {  
      // TODO: Add your control notification handler code here  
      CClientSend send;  
      send.DoModal();  
 }