HOWTO: Programmatically Detect RAS Installation on Workstation

• Microsoft Windows 95
• Microsoft Windows NT Workstation version 4.0

SUMMARY

This article shows how to programmatically detect if RAS is installed on a Workstation.

The sample code included in this article takes into account that RAS might not be installed, even if a copy of the rasapi32.dll exists in the system directory. Also a valid phone book entry and an active modem are not required.

MORE INFORMATION

There are two parts to the code because there are two scenarios that you may encounter. In the first scenario, RAS is not installed and its corresponding dll, rasapi32.dll, is not available in the system folder. The way to detect this is to do a LoadLibrary() on the "rasapi32". If the LoadLibrary() fails then RAS is not installed.

If LoadLibrary() succeeds, it does not guarantee that RAS is installed. Rasapi32.dll and rasapi32.lib may have been copied into the corresponding folders without actually installing RAS. To check for this scenario, after loading rasapi32, call the RasDial() function asynchronously and see if it returns a valid error number.

The code below demonstrates one way to do this. The phone book entry name contains NULL to ensure that a valid entry name is not a requirement to run this sample. The first time the RasDial callback function is called with a successful message the waiting event is signaled so that RasHangUp will be called.

Sample Code

   /*
   *   RasDialAsync.c
   *
   *       Usage: RasDialAsync
   *
   *   This is a console application sample that detects
   *   if RAS is installed.
   *
   *   RasDialFunc() is the callback function for asynchronous RasDial().
   *
   */
   
   
   #define WIN32_LEAN_AND_MEAN
   
   #include <stdio.h>
   #include <windows.h>
   #include <ras.h>
   #include <raserror.h>
   #include <string.h>
   #include <winbase.h>
   
   
   void WINAPI RasDialFunc(UINT unMsg,
                           RASCONNSTATE rasconnstate,
            DWORD dwError );
   
   HANDLE Event_handle; // Global event handle.
   HINSTANCE hDLL;      // Handle to DLL.
   FARPROC lpfnDllFunc1, lpfnDllFunc2,
      lpfnDllFunc3, lpfnDllFunc4;  // Function pointers.
   
   
   /* Begin main()... */
   
   int main(int argc, char*argv[])
   {
      RASDIALPARAMS Myrasdialparams; // Structure to store the RasDial
                                     // parameters.
      RASCONNSTATUS mystate;   // Buffer to receive status data.
      HRASCONN hRasConn;       // Handle to RAS connection.
      DWORD retval;            // Return value from a function.
      LPCTSTR MyRasDialEvent;  // Pointer to the event name.
      char ch;
   
   
      // Create the event MyRasDialEvent, which indicates completion of
      // RasDial().
      Event_handle = CreateEvent(NULL, FALSE, FALSE, MyRasDialEvent);
      if (!Event_handle)
      {
         printf("Error in CreateEvent - %d", GetLastError());
         return -1;
      }
   
      hDLL = LoadLibrary("rasapi32");
      if (hDLL != NULL)
      {
         lpfnDllFunc1 = (FARPROC)GetProcAddress(hDLL, "RasDialA");
         if (!lpfnDllFunc1)
         {
            FreeLibrary(hDLL);
            return -1;
         }
   
         lpfnDllFunc2 = (FARPROC)GetProcAddress(hDLL,
   "RasGetConnectStatusA");
         if (!lpfnDllFunc2)
         {
            FreeLibrary(hDLL);
            return -1;
         }
   
         lpfnDllFunc3 = (FARPROC)GetProcAddress(hDLL, "RasHangUpA");
         if (!lpfnDllFunc3)
         {
            FreeLibrary(hDLL);
            return -1;
         }
   
         lpfnDllFunc4 = (FARPROC)GetProcAddress(hDLL,
   "RasGetErrorStringA");
         if (!lpfnDllFunc4)
         {
            FreeLibrary(hDLL);
            return -1;
         }
   
   
         // Initialize the RASDIALPARAMS structure.
         Myrasdialparams.dwSize =sizeof(RASDIALPARAMS);
         lstrcpy(Myrasdialparams.szEntryName, "");
         lstrcpy(Myrasdialparams.szPhoneNumber, "12345");
         lstrcpy(Myrasdialparams.szCallbackNumber, "");
         lstrcpy(Myrasdialparams.szUserName, "abcd");
         lstrcpy(Myrasdialparams.szPassword, "xxx");
         lstrcpy(Myrasdialparams.szDomain, "pqr");
   
         // Dial out asynchronously using RasDial()
         printf("Dialing.\n");
         hRasConn = NULL;
   
         retval = lpfnDllFunc1(NULL, NULL, &Myrasdialparams, 0,
   &RasDialFunc, &hRasConn);
         // Check whether RasDial() succeeded
         if (retval)
         {
            printf("RasDial retval = %d\n", retval);
            return -1;
         }
   
         // The connection has been established. Now break the
         // connection.
   
         // Wait for the RasDial() to complete, signaled by the
         // SetEvent().
         retval = WaitForSingleObject(Event_handle, 30000);
         switch (retval)
         {
            case WAIT_OBJECT_0: // Normal completion of RasDial
               printf("Calling RasHangUp...\n");
               lpfnDllFunc3(hRasConn);
               mystate.dwSize = sizeof(RASCONNSTATUS);
               while(TRUE)
               {
                  if (ERROR_INVALID_HANDLE ==
   lpfnDllFunc2(hRasConn,&mystate))
                  break;
                  Sleep(0);
               }
               break;
            case WAIT_TIMEOUT: // RasDial timed out
               printf("RasDial Timed out...");
               break;
         }
         scanf("%c", &ch);
         return 1;
      }
      else
      {
         printf("Ras is not installed/n");
         return 1;
      }
   
   }
   // End main().
   
   // Callback function RasDialFunc().
   void WINAPI RasDialFunc(UINT unMsg,
            RASCONNSTATE rasconnstate,
            DWORD dwError )
   {
      char szRasString[256]; // Buffer for storing the error string.
   
       if ( dwError )  // Error occurred.
         {
           printf ("Error: %d - ", dwError);
           lpfnDllFunc4( (UINT)dwError, szRasString, 256 );
         printf("%s\n", szRasString);
         SetEvent(Event_handle);
         return;
         }
   
       switch (rasconnstate)
       {
           case RASCS_OpenPort:
               printf ("RASCS_OpenPort = %d\n", rasconnstate);
               printf ("Opening port.\n");
            SetEvent(Event_handle);
          break;
           default:
               break;
       } // End switch.
   } // End RasDialFunc().

Keywords          : NtwkRAS
Version           : WIN95; WINNT:4.0
Platform          : Win95 winnt
Issue type        : kbhowto