Programming

Hi,
Can any one please help me with this. Am struggling hard to get a solution.

I am doing telnet through a C program and getting the stdout file descriptor of the remote machine to pipe.

read() function is getting data, But whenl it receives SOH character ie. ^A ( Start of heading = Console Interrupt) read() is unable to get the characters which are mentioned after the SOH. Even on next read() it is unable to get the data.

My program works fine if I do telnet from a Solaris machine to another Solaris machine.

But the above problem in read() is coming when I do telnet from Solaris machine to a Linux machine. Only on the Linux machine the SOH character is prompted.

I will appreciate if somebody can give some soltuion.

Cheers,
JDS

I can't tell for sure without reading the code, but my guess would be that the pipe is blocking, waiting for a newline.

You can set the pipe to nonblocking with:

Code:

#include <unistd.h>
#include <fcntl.h> 

...

// Create pipe
pipe(pvals);
// Set both ends of pipe to nonblocking
for(n=0; n<2; n++)
{
  // Get previous flags
  int f = fcntl(pvals[n], F_GETFL, 0);
  // Set bit for non-blocking flag
  f |= O_NONBLOCK;
  // Change flags on fd
  fcntl(pvals[n], F_SETFL, f);
}

Thanks Corona

I have done the code changes as per your suggestion with slight changes and the read() function is now working fine.

But am getting problem in select() function on pipe's file descriptor as mentioned below:

Once, telnet is done to remote machine am able to read it's stdout with "login" prompt which is directed to my local machine's pipe.

After this I write() the username on another pipe which is being read by the remote machine. On second select() + read() it doesnot bring the "password" prompt as it should for normal telnet case.

Can any one suggest why select() is getting blocked once the read() and write() has successfully completed.