#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string.h>
 
#ifndef   NI_MAXHOST
#define   NI_MAXHOST 1025
#endif

static void die(const char *msg)
{
	printf("%s\n", msg);
	exit(1);
}

int main(void)
{
	int err;

	struct addrinfo *res, hints = {
		.ai_family = AF_INET6,
		.ai_socktype = SOCK_STREAM,
		.ai_flags = AI_PASSIVE
	};

	/* set up the server socket (listen on ::) */
	err = getaddrinfo(NULL, "8080", &hints, &res);
	if (err)
                die(gai_strerror(err));
 
	int sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
	if (sock < 0)
		die(strerror(errno));

	err = bind(sock, res->ai_addr, res->ai_addrlen);
	if (err)
		die(strerror(errno));

	err = listen(sock, 10);
	if (err)
		die(strerror(errno));

	freeaddrinfo(res);

	err = fcntl(sock, F_SETFD, FD_CLOEXEC);
	if (err)
                die(strerror(errno));

	pid_t child = fork();
	if (child < 0)
		die(strerror(errno));

	if (child == 0) {
		/* the child connects to the server socket and starts writing data to it */
		hints.ai_flags = 0;
		err = getaddrinfo("fe80::216:d3ff:fece:57d9%eth0", "8080", &hints, &res);
		if (err)
			die(gai_strerror(err));
		
		int fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
		if (fd < 0)
			die(strerror(errno));
		
		err = connect(fd, res->ai_addr, res->ai_addrlen);
		if (err)
			die(strerror(errno));
		
		freeaddrinfo(res);
		
		for (;;) {
			const char buffer[4*1024];
			err = write(fd, buffer, sizeof(buffer));
			if (err < 0)
				die(strerror(errno));
			printf("child: wrote %d bytes\n", err);
		}
	} else {
		/* the server accepts the connection and starts reading from it */
		struct sockaddr_in6 sin6;
		socklen_t socklen = sizeof(sin6);
		int clientfd = accept(sock, (struct sockaddr *) &sin6, &socklen);
		if (clientfd < 0)
			die(strerror(errno));
		
		char hostname[NI_MAXHOST] = "";
		err = getnameinfo((struct sockaddr *)&sin6, socklen, hostname, NI_MAXHOST, NULL, 0, 0); 
		printf("hostname: %s\n", hostname);

		fd_set readfds;
		FD_ZERO(&readfds);
		FD_SET(clientfd, &readfds);

		for (;;) {
			err = select(clientfd + 1, &readfds, NULL, NULL, NULL);
			if (err < 0)
				die(strerror(errno));

			char buffer[4*1024];
			err = read(clientfd, buffer, sizeof(buffer));
			printf("parent: read %d bytes\n", err);

			FD_SET(clientfd, &readfds);
		}
	}
	
	return 0;
}