Interrupt-Driven Socket I/O

The SIGIO signal notifies a process when a socket (actually any file descriptor) has finished a data transfer. The steps in using SIGIO are:

• Set up a SIGIO signal handler with thesignal(3C) or sigvec(3UCB) calls.

• Use fcntl(2) to set the process ID or process group ID to route the signal to its own process ID or process group ID (the default process group of a socket is group 0).

• Convert the socket to asynchronous, as shown in "Asynchronous Socket I/O".

Example 2-15 shows some sample code to allow a given process to receive information on pending requests as they occur for a socket. With the addition of a handler for SIGURG, this code can also be used to prepare for receipt of SIGURG signals.

Example 2-15 Asynchronous Notification of I/O Requests

#include <fcntl.h>
#include <sys/file.h>
 ...
signal(SIGIO, io_handler);
/* Set the process receiving SIGIO/SIGURG signals to us. */
if (fcntl(s, F_SETOWN, getpid()) < 0) {
		perror("fcntl F_SETOWN");
		exit(1);
}