#include <err.h>
#include <netdb.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <string.h>

int main(int argc, char **argv) {
	if (argc != 2)
		errx(1, "Usage: %s <port>\n", argv[0]);

	int port = strtol(argv[1], NULL, 10);
	if (port < 0 || port > 65535)
		errx(1, "bad port");

	struct sockaddr_in sin;
	memset(&sin, 0, sizeof(sin));
	sin.sin_family = AF_INET;
	sin.sin_addr.s_addr = INADDR_ANY;
	sin.sin_port = htons(port);

	int s;

	if ((s = socket(PF_INET, SOCK_STREAM, 0)) == 0)
		err(1, "socket");

	if (bind(s, (struct sockaddr*)&sin, sizeof(sin)) != 0)
		err(1, "bind");

	if (listen(s, 10) != 0)
		err(1, "listen");

	int ss;
	int count = 0;
	while ((ss = accept(s, 0, 0)) != -1)
		printf("Opened %d sockets\n", ++count);

	if (ss == -1)
		err(1, "accept");

	return 0;
}