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Serial Port  Communications

Posted on 1998-01-29
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Last Modified: 2013-12-03
I have a program that I want to dial a number, however when I run the program nothing happens.Please tell me whats wrong with this code.
#include<windows.h>
#include<windowsx.h>
#include<iostream.h>
void main()
{
      DCB *dcb;
char jess[31]="ATDP 169";
char *jesse=jess;
int dummy;
HANDLE hComm;
hComm = CreateFile( "COM2",  
                    GENERIC_READ | GENERIC_WRITE,      
                              0,
                    0,
                              OPEN_EXISTING,
                    FILE_FLAG_WRITE_THROUGH,
                    0);
cout<<"Handle to Com2 opened!\n";
cout<<"Dialing test!\n";
GetCommState(hComm,dcb);
SetCommState(hComm,dcb);
WriteFile(hComm,jesse,strlen(jesse),0,NULL);
cin>>dummy;
CloseHandle(hComm);
cout<<"Closed!";
}
0
Comment
Question by:laeuchli
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4 Comments
 
LVL 7

Accepted Solution

by:
galkin earned 10 total points
ID: 1410604
Lok at documentation of WriteFile. This is extract from there "...If lpOverlapped is NULL, lpNumberOfBytesWritten cannot be NULL...". Forth and the fifth parameters cannot be NULL together.
Besides strlen returns string length EXCLUDING '\0' character so correct string length is strlen() + 1.
0
 
LVL 22

Expert Comment

by:nietod
ID: 1410605
Although the rest of your answer is surely right, I'm not sure why you are suggesting there might be a problem with the string length.  There is a problem only if he wants to send the NUL character and this is unlikely.
0
 
LVL 3

Expert Comment

by:stefanr
ID: 1410606
How about adding a '\r' to the dial string, i.e.
char jess[31]="ATDP 169\r";

/Stefan
0
 
LVL 3

Expert Comment

by:stefanr
ID: 1410607
...and (oops!) change
DCB *dcb;
to
DCB dcb;
and
GetCommState(hComm,dcb);
to
GetCommState(hComm,&dcb);
and similar to SetCommState.
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