File Descriptor for socket not working - c

Question

Here is the code i am using. Whenever i write something to the Stdin, it works, but it is not working for socket. It's not able to enter the loop for Socket. I am new to socket programming.
void HandleConnection(int socket)
{
fd_set rfd;
struct timeval tv;
int retval;
printf("%d",socket);
MakeNonBlocking(socket);
/* Watch stdin (fd 0) to see when it has input. */
FD_ZERO(&rfd);
while(1)
{
FD_SET(STDIN, &rfd);
FD_SET(socket, &rfd);
/* Wait up to five seconds. */
tv.tv_sec = 50;
tv.tv_usec = 0;
retval = select(2, &rfd,NULL, NULL, &tv);
if(retval == 0)
{
printf("No data within fifty seconds.\n");
exit(1);
}
if(FD_ISSET(socket,&rfd))
{
printf("socket wala\n");
recieve_message(&socket);
send_message(&socket);
}
if(FD_ISSET(STDIN,&rfd))
{
printf("stdin wala\n");
recieve_message(&socket);
send_message(&socket);
}
}
}

Answer 1

FDZERO must go before FDSET inside the loop
select(2, ...) should be select(highest filedescriptor +1, ...).
when select returns you should check for negative value in case of errors
you should consider using pselect instead of select.
Clear tv before you reinitialize it.

Answer 2

It appears that you don't understand how the nfds argument to select() is used. The man page addresses this explicitly:
The first nfds
descriptors are checked in each set; i.e., the descriptors from 0 through nfds-1 in the descriptor sets are examined. (Example:
If you have set two file descriptors "4" and "17", nfds should not be "2", but rather "17 + 1" or "18".)
So here is how you should rewrite your code.
int maxfd = (socket > STDIN ? socket : STDIN) + 1; /* select() requires the number of FDs to scan, which is max(fds)+1 */
while(1){
FD_ZERO(&rfd); /* This needs to be done each time through the loop */
/* Watch stdin (fd 0) to see when it has input. */
FD_SET(STDIN, &rfd);
FD_SET(socket, &rfd);
/* Wait up to five seconds. */
tv.tv_sec = 50;
tv.tv_usec = 0;
retval = select(maxfd, &rfd,NULL, NULL, &tv);
if(retval == 0)
{
printf("No data within fifty seconds.\n");
exit(1);
}
if(retval == -1) /* Check for error */
{
perror("Error from select");
exit(2);
}
if(FD_ISSET(socket,&rfd))
{
printf("socket wala\n");
recieve_message(&socket);
send_message(&socket);
}
if(FD_ISSET(STDIN,&rfd))
{
printf("stdin wala\n");
recieve_message(&socket);
send_message(&socket);
}
}