#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define	REVEAL	(4523)

#define	Q1(x)	(((x)>>24)&0xFF)
#define	Q2(x)	(((x)>>16)&0xFF)
#define	Q3(x)	(((x)>>8)&0xFF)
#define	Q4(x)	(((x)>>0)&0xFF)

int main (int argc, char **argv) {
	int s0, s1;			/* sockets */
	unsigned long h;
	int c, len;
	char s[32];
	struct sockaddr_in name;

	if ((s0 = socket (PF_INET, SOCK_STREAM, 0)) < 0) {
		perror ("Socket create");
		exit (1);
	}
	name.sin_family = AF_INET;
	name.sin_port = htons (REVEAL);
	name.sin_addr.s_addr = htonl (INADDR_ANY);
	if (bind (s0, (struct sockaddr *) &name, (int) (sizeof (name))) < 0) {
		perror ("socket bind");
		exit (2);
	}
	if (listen (s0, 1) < 0) {
		perror ("socket listen");
		exit (3);
	}
	switch (c = fork()) {
		case -1:
			perror ("fork");
			exit (4);
		case 0:
			setpgid (0, 0);
			while (1) {
				len = (int) sizeof (name);
				if ((s1 = accept (s0, (struct sockaddr *) &name, (socklen_t *) &len)) < 0) {
					fprintf (stderr, "ERRNO: %d\n", errno);
					perror ("socket accept");
					break;
				}
				h = ntohl (name.sin_addr.s_addr);
				len = sprintf (s, "%d.%d.%d.%d:%u\n", Q1(h), Q2(h), Q3(h), Q4(h), ntohs (name.sin_port));
				write (s1, s, len);
				close (s1);
			}
		default:
			exit (0);
	}
}