unpv13e/oob/heartbeatcli.c

#include	"unp.h"

static int		servfd;
static int		nsec;			/* #seconds betweeen each alarm */
static int		maxnprobes;		/* #probes w/no response before quit */
static int		nprobes;		/* #probes since last server response */
static void	sig_urg(int), sig_alrm(int);

void
heartbeat_cli(int servfd_arg, int nsec_arg, int maxnprobes_arg)
{
	servfd = servfd_arg;		/* set globals for signal handlers */
	if ( (nsec = nsec_arg) < 1)
		nsec = 1;
	if ( (maxnprobes = maxnprobes_arg) < nsec)
		maxnprobes = nsec;
	nprobes = 0;

	Signal(SIGURG, sig_urg);
	Fcntl(servfd, F_SETOWN, getpid());

	Signal(SIGALRM, sig_alrm);
	alarm(nsec);
}

static void
sig_urg(int signo)
{
	int		n;
	char	c;
 
	if ( (n = recv(servfd, &c, 1, MSG_OOB)) < 0) {
		if (errno != EWOULDBLOCK)
			err_sys("recv error");
	}
	nprobes = 0;			/* reset counter */
	return;					/* may interrupt client code */
}

static void
sig_alrm(int signo)
{
	if (++nprobes > maxnprobes) {
		fprintf(stderr, "server is unreachable\n");
		exit(0);
	}
	Send(servfd, "1", 1, MSG_OOB);
	alarm(nsec);
	return;					/* may interrupt client code */
}