Simple server client UDP Socket program

• Download SimpleUDP - 2.21 MB

Introduction

This is a simple application demonstrating UDP client server in MFC.There are many examples related to TCP but very few for UDP. So,I thought of making simple application and uploading it
here.

Background

The main Dialog act as a server. Server will keep on waiting for data on a particular port, it receives the data and display. The client is started on clicking start button of main dialog. It can send data to server. Server receives the data and display it.

Using the code

The Main Dialog class CSimpleUDPDlg acts as a server. A thread is started in OnInitDialog() of man dialog to receive the data send by client.

Code snippet of CSimpleUDPDlg.cpp and CClientSend.cpp is shown below.

 #include "afxsock.h" 
//Add global variables 
    HANDLE thr;
    unsigned long id1; 
 // Definition of Thread ReceiveData shown below. 

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

    //start a thread to receive data send by client 
    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
}     
//The client dialog is started in OnStart() function  

void CSimpleUDPDlg::OnStart() 
{
    // TODO: Add your control notification handler code here
    CClientSend send;
    send.DoModal();
}

     
//Code Snippet of CClientSend.cpp is shown below which is a simple dialog class. 
#include "afxsock.h" 

void CClientSend::OnSend() 
{
    // TODO: Add your control notification handler code here
    AfxSocketInit( NULL);
    CString Buffer;
    m_editsend.GetWindowText(Buffer);
    int buflen=strlen(Buffer);

     CSocket echoClient;  

     if (echoClient.Create(0,SOCK_DGRAM,NULL) == 0) {
    AfxMessageBox("Create() failed");
    }
// in place of localhost we can give IP Address of the Particular machine.
     if (echoClient.SendTo(Buffer, buflen,514,
      (LPCSTR)"localhost", 0) != buflen) {
    AfxMessageBox("SendTo() sent a different number of bytes than expected");
  }

     echoClient.Close();

} 

Points of Interest

Well this is my first Article,hope it would be helpful.