heartbeat-server.c

Linux socket 编程

/* heartbeat-server.c
 *
 * Copyright (c) 2000 Sean Walton and Macmillan Publishers.  Use may be in
 * whole or in part in accordance to the General Public License (GPL).
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
*/

/*****************************************************************************/
/*** heartbeat-server.c                                                    ***/
/***                                                                       ***/
/*** Demonstrates how to keep track of the server using a "heartbeat".  If ***/
/*** the heartbeat is lost, the connection can be reestablished and the    ***/
/*** session resumed.                                                      ***/
/*****************************************************************************/

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <resolv.h>
#include <signal.h>

int client;
struct sigaction act;

/*---------------------------------------------------------------------*/
/*--- sig_handler - catch and send heartbeat.                       ---*/
/*---------------------------------------------------------------------*/
void sig_handler(int signum)
{
	if ( signum == SIGURG )
	{   char c;
		recv(client, &c, sizeof(c), MSG_OOB);
		if ( c == '?' )				   /* Are you alive? */
			send(client, "Y", 1, MSG_OOB);		/* YES! */
	}
	else if ( signum == SIGCHLD )
		wait(0);
}

/*---------------------------------------------------------------------*/
/*--- servlet - process requests                                    ---*/
/*---------------------------------------------------------------------*/
void servlet(void)
{	int bytes;
	char buffer[1024];

	bzero(&act, sizeof(act));
	act.sa_handler = sig_handler;
	act.sa_flags = SA_RESTART;
	sigaction(SIGURG, &act, 0);	/* connect SIGURG signal */
	if ( fcntl(client, F_SETOWN, getpid()) != 0 )
		perror("Can't claim SIGIO and SIGURG");
	do
	{
		bytes = recv(client, buffer, sizeof(buffer), 0);
		if ( bytes > 0 )
			send(client, buffer, bytes, 0);
	}
	while ( bytes > 0 );
	close(client);
	exit(0);
}

/*---------------------------------------------------------------------*/
/*--- main - set up client and begin the heartbeat.                 ---*/
/*---------------------------------------------------------------------*/
int main(int count, char *strings[])
{	int sd;
	struct sockaddr_in addr;

	if ( count != 2 )
	{
		printf("usage: %s <port>\n", strings[0]);
		exit(0);
	}
	bzero(&act, sizeof(act));
	act.sa_handler = sig_handler;
	act.sa_flags = SA_NOCLDSTOP | SA_RESTART;
	if ( sigaction(SIGCHLD, &act, 0) != 0 )
		perror("sigaction()");

	sd = socket(PF_INET, SOCK_STREAM, 0);
	bzero(&addr, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_port = htons(atoi(strings[1]));
	addr.sin_addr.s_addr = INADDR_ANY;
	if ( bind(sd, (struct sockaddr*)&addr, sizeof(addr)) != 0 )
		perror("bind()");

	listen(sd, 15);
	for (;;)
	{
		client = accept(sd, 0, 0);
		if ( client > 0 )
		{
			if ( fork() == 0 )
			{
				close(sd);
				servlet();
			}
			else
				close(client);
		}
		else
			perror("accept()");
	}
	close(sd);
	return 0;
}