web server+Ӧ

This Unix C code monitors a web server every few minutes by trying to retrieve its home page. It sen

/*
 by Network Wizards, 1995  (www.nw.com)

 webcheck servername mailaddr

 every minute,
   sends GET / HTTP/1.0 to server, port 80
   reads response
   if no answer, calls pmail to send a page
*/

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/time.h>
#include <signal.h>
#include <sys/param.h>
#include <sys/ioctl.h>

#define FALSE 0
#define TRUE  1

#define	PORT            80

#define	MAXTMPLEN	128	/* max length of tmp array declared below */

#define BUFLEN  256
char buf[BUFLEN];


struct hostent *hp;
int skt;
FILE *fin, *fout;

struct itimerval tv;

void tout();
char tmp[MAXTMPLEN];
char *mailaddr;

main(argc, argv)
  int argc;
  char *argv[];
{
  int i, c, down;

  /* punt if syntax is wrong */
  if (argc != 3)
  {
    fprintf(stderr,"usage: wwwtest server email\n");
    exit(1);
  }
  if ((hp = gethostbyname(argv[1])) == NULL)
  {
    fprintf(stderr,"can't find host '%s'.\n",argv[1]);
    exit(1);
  }
  mailaddr = argv[2];

  if (fork())
    exit(0);
  for (i = 10; i >= 0; i--)
    (void) close(i);
  (void) open("/dev/null", O_RDONLY);
  (void) dup2(0, 1);
  (void) dup2(0, 2);
  i = open("/dev/tty", O_RDWR);
  if (i > 0)
    {
    (void) ioctl(i, TIOCNOTTY, (char *)NULL);
    (void) close(i);
  }

  signal(SIGALRM,tout);

  down = FALSE;
  for (;;)
  {
    if (checkserver())     /* if server up */
    {
      if (down)
	notify("up",argv[1]);
      down = FALSE;
      sleep(60);
      continue;
    }
    /* if server down */
    sleep(5*60);
    if (checkserver())   /* try once more */
    {
      sleep(60);
      continue;
    }
    notify("down",argv[1]);
    down = TRUE;
    sleep(3*60);
  }
}

checkserver()
{
  struct sockaddr_in sin;
  u_long addr;

  tv.it_interval.tv_sec  = 0;
  tv.it_interval.tv_usec = 0;
  tv.it_value.tv_sec     = 30;
  tv.it_value.tv_usec    = 0;
  setitimer(ITIMER_REAL,&tv,NULL);

  /* create a socket */
  if ((skt = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
  {
    cancel_timeout();
    return(FALSE);
  }

  sin.sin_family = hp->h_addrtype;
  bcopy (hp->h_addr, &sin.sin_addr, hp->h_length);
  addr = ntohl(sin.sin_addr.s_addr);
  sin.sin_port = htons(80);

  /* Now, connect to that port */
  if (connect(skt, (struct sockaddr *) &sin, sizeof(sin)) < 0)
  {
    close(skt);
    cancel_timeout();
    return(FALSE);
  }

  /* associate a STREAM to 'fin' and 'fout' from 'skt' */
  if ((fin = fdopen(skt, "r")) == NULL ||
      (fout = fdopen(skt, "w")) == NULL)
  {
    close(skt);
    cancel_timeout();
    return(FALSE);
  }

  /* write out the request to the server (remember to terminate 
   * with <return><newline>).
   */
  fprintf(fout, "GET / HTTP/1.0\r\n\r\n");
  fflush(fout);

  /* read back results */
  while (fgets(buf,BUFLEN,fin) != NULL)
  {
    if (!strncasecmp(buf,"HTTP/1.0 200 OK",15))
    {
      fclose(fin); fclose(fout);
      close(skt);
      cancel_timeout();
      return(TRUE);
    }
    if (*buf == '\r') break;
    if (*buf == '\n') break;
  }
  fclose(fin); fclose(fout);
  close(skt);
  cancel_timeout();
  return(FALSE);
}

cancel_timeout()
{
  tv.it_interval.tv_sec  = 0;
  tv.it_interval.tv_usec = 0;
  tv.it_value.tv_sec     = 0;
  tv.it_value.tv_usec    = 0;
  setitimer(ITIMER_REAL,&tv,NULL);
}

void tout()
{
  fclose(fin); fclose(fout);
  close(skt);
  skt = -1;
}

notify(msg,server)
  char *msg, *server;
{
  char buf[256];

  sprintf(buf,"echo \"%s : %s\" | /usr/bin/Mail %s",
	  msg,server,mailaddr);
  system(buf);
}