Re: Readfile hangs while trying to read the response from printer

From:

"AliR $VC++ MVP$" <AliR@online.nospam>

Newsgroups:

microsoft.public.vc.mfc,microsoft.public.win32.programmer.ui,comp.os.ms-windows.programmer.win32

Date:

Thu, 10 Jan 2008 09:50:49 -0600

Message-ID:

<Ndrhj.3817$El5.3054@newssvr22.news.prodigy.net>

What do you mean by hangs? Are you sure there is any data coming in from
the port? If there is no data in the receive buffer then ReadFile will just
sit there. until there is data to be read.

Also you might want to poll the port for data, in a worker thread before
reading from it.

AliR.

"hari" <haricibi83@gmail.com> wrote in message
news:722ce690-2dde-4acd-ad74-93b772f9cec7@v46g2000hsv.googlegroups.com...

Hi all,
      Im trying to send a comamnd to the printer and read the
response for it thru parallel port(LPT1:). The write file always
succeeds, but in readfile it goes to hanging state. I have given my
code below.

int g;
HANDLE h;
DWORD NumberOfBytesWritten,NumberOfBytesRead;
unsigned char buff1[12];
unsigned char buff_read[30];

h = CreateFile("LPT1:",
                      GENERIC_READ | GENERIC_WRITE,
                      FILE_SHARE_READ,
                      NULL,
                      OPEN_ALWAYS,
                      FILE_ATTRIBUTE_NORMAL |
                      FILE_FLAG_SEQUENTIAL_SCAN,
                      NULL);
if (h == INVALID_HANDLE_VALUE)
{
  g= 0;
  return 0;
}
else
{

g=1;
  buff1[0] = '{';
  buff1[1] = 'W';
  buff1[2] = 'B';
  buff1[3] = '|';
  buff1[4] = '}';

i = WriteFile(h,buff1,5,&NumberOfBytesWritten ,NULL);
i =ReadFile(h,buff_read,2,&NumberOfBytesRead,NULL);
CloseHandle(h);
return 400;
}