Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Waitforsingleobject always results in a timeout !!!

Posted on 2004-08-03
1
Medium Priority
?
2,072 Views
Last Modified: 2013-12-03
My waitforsingleobject always results in a timeout and i am unable to figure out why.. Please look at my code below..
i have a read file call .that gets called as soon as i receive a character in the input buffer. Hence i am waiting on waitcommevent and when a character appears, i issue a readfile to read all the characters that have come through my serial port.. However, waitcommevent is a blocking call. I had to make the waitcommevent timeout.. Hence, i moved to overlapped IO. But now..my waitcommevent always timeouts even though i know that there are characters to read. Please let me know what is wrong with my code..
/*********************************************************************************************/
int ReadProc1(char *str)
{
     
     /*
     Using the EV_RXCHAR flag will notify the thread that a byte arrived at the port. This event,
     used in combination with the ReadFile function, enables a program to read data only after
     it is in the receive buffer, as opposed to issuing a read that waits for the data to arrive*/


     DWORD dwCommEvent; //a variable that receives a mask indicating the type of event that occurred
     char chRead;          // Character read every time a read takes place.
     DWORD dwRead =0,Err,Bytes;          //Pointer to the variable that receives the number of bytes read
     char * str =calloc(100,sizeof(char));
     unsigned int i=0,j=2;
     BOOL fWaitingOnRead = FALSE,Ok= FALSE;

     OVERLAPPED osReader= {0};

     

     FillMemory(str, strlen(str), 0);
     //if((strcmp(p->PType,"13") == 0) && (strcmp(p->Data,"0") != 0)) stop = 0x06;
     if (stop == 0x06) terminate=1;
     if (stop == 0x03) terminate=0;
     
     
     memset(&osReader,0,sizeof(OVERLAPPED));
     osReader.hEvent = CreateEvent(
    NULL,   // no security attributes
    TRUE,  // auto reset event
    FALSE,  // not signaled
    NULL    // no name
    );
     if (osReader.hEvent == NULL)
     {
          LogEvent(hComm,"Error creating overlapped event");
     }

     for ( ; ; ) {
          if (!fWaitingOnRead)
          {

               if (!(WaitCommEvent(hComm, &dwCommEvent,&osReader)))
               {

                    if (GetLastError() != ERROR_IO_PENDING)
                    {
                         LogEvent (ghwnd," Error in Wait Comm Event");
                         return FALSE;
                    }
                    else
                    {
                         fWaitingOnRead = TRUE;
                         Err = WaitForSingleObject(hComm, READ_TIMEOUT);
                         
                         switch(Err)
                         {
                         case WAIT_TIMEOUT:
                              LogEvent(ghwnd,"Timed out waiting for response from device.. check connections/power");
                              return FALSE;
                              break;


                         case WAIT_OBJECT_0:
                          // Event triggered. Check the status.
                             
                              Ok = GetOverlappedResult(hComm, &osReader, &Bytes, TRUE);
                              if (Ok)
                              {
                       
                                   do
                                   {
                                                           
                                        if (ReadFile(hComm, &chRead, 1, &dwRead, NULL))
                                        {
                                   
                                             // A byte has been read; process it.
                                             str[i++]=chRead;
                                                                                     }
                                        else
                                        {
                                        // An error occurred in the ReadFile call.
                                             LogEvent(ghwnd," Read Failed With Error Code ");
                                             break;
                                        }
                         
                                   } while (dwRead );
                              }
                              else
                              {
                                   LogEvent(ghwnd,"Get Overlapped Result Failed ");
                                   return FALSE;
                              }
                              break;
                         default:

                              LogEvent (ghwnd," Error in wait for single object");
                              return FALSE;
                              break;
                         }//End of Switch
                    }//End of GetLastError
               }
               else
               {
                    LogEvent(ghwnd,"Read Completed Immedialtely");
                       /* So Proceed to readfile
                                 }//End of Wait Comm Event
          }// End of Waiting on Read
         
     
     }

         
     }
     
 
/*********************************************************************************************
0
Comment
Question by:shubha_mohan
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
1 Comment
 
LVL 48

Accepted Solution

by:
AlexFM earned 1000 total points
ID: 11704971
0

Featured Post

[Webinar] Lessons on Recovering from Petya

Skyport is working hard to help customers recover from recent attacks, like the Petya worm. This work has brought to light some important lessons. New malware attacks like this can take down your entire environment. Learn from others mistakes on how to prevent Petya like worms.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article shows how to make a Windows 7 gadget that accepts files dropped from the Windows Explorer.  It also illustrates how to give your gadget a non-rectangular shape and how to add some nifty visual effects to text displayed in a your gadget.…
Entering time in Microsoft Access can be difficult. An input mask often bothers users more than helping them and won't catch all typing errors. This article shows how to create a textbox for 24-hour time input with full validation politely catching …
This is Part 3 in a 3-part series on Experts Exchange to discuss error handling in VBA code written for Excel. Part 1 of this series discussed basic error handling code using VBA. http://www.experts-exchange.com/videos/1478/Excel-Error-Handlin…
Want to learn how to record your desktop screen without having to use an outside camera. Click on this video and learn how to use the cool google extension called "Screencastify"! Step 1: Open a new google tab Step 2: Go to the left hand upper corn…

670 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question