#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>   /* for getservbyname */
#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <sys/wait.h>

char *progname;
int s;                              /* file descriptor */
void death_of_child(int sig);

int main(int argc, char **argv)
{
	struct sockaddr_in address;
	char buffer[INET_ADDRSTRLEN];   /* for inet_pton */
	struct hostent *entry;          /* for gethostbyname, gethostbyaddr */
	pid_t pid;
	int c;

	progname = argv[0];
	bzero((char *)&address, sizeof address);
	address.sin_family = AF_INET;

	if (argc == 2) {   /* one command line argument */
		const struct servent *const p = getservbyname("telnet", "tcp");
		if (p == NULL) {
			fprintf(stderr, "%s: couldn't find telnet port number\n",
				progname);
			return 1;
		}
		address.sin_port = p->s_port;
	}

	else if (argc == 3) {   /* two command line arguments */
		if (sscanf(argv[2], "%hd", &address.sin_port) != 1) {
			fprintf(stderr, "%s: %s is not a legal port number\n",
				progname, argv[2]);
			return 2;
		}
		address.sin_port = htons(address.sin_port);
	}

	else {
		fprintf(stderr, "%s: usage hostname [port]\n", progname);
		return 3;
	}

	entry = gethostbyname(argv[1]);
	if (entry == NULL) {
		fprintf(stderr, "%s: gethostbyname, h_errno == %d\n",
			progname, h_errno);
		return 4;
	}
	address.sin_addr.s_addr = *(in_addr_t *)entry->h_addr_list[0];

	s = socket(AF_INET, SOCK_STREAM, 0);
	if (s < 0) {
		perror(progname);
		return 5;
	}

	if (inet_ntop(AF_INET, &address.sin_addr, buffer, sizeof buffer) == NULL) {
		perror(progname);
		return 6;
	}
	printf("Trying %s...\n", buffer);

	if (connect(s, (struct sockaddr *)&address, sizeof address) != 0) {
		perror(progname);
		return 7;
	}

	entry = gethostbyaddr((char *)&address.sin_addr, sizeof address.sin_addr,
		AF_INET);
	if (entry == NULL) {
		fprintf(stderr, "%s: gethostbyaddr, h_errno == %d\n",
			progname, h_errno);
		return 8;
	}
	printf("Connected to %s.\n", entry->h_name);

	if (signal(SIGCHLD, death_of_child) == SIG_ERR) {
		perror(progname);
		return 9;
	}

	pid = fork();
	if (pid < 0) {
		perror(progname);
		return 10;
	}

	if (pid == 0) {
		/* Arrive here if I am the child.
		Copy from the server to the stdout. */

		char c;
		while (read(s, &c, 1) == 1) {
			putchar(c);
		}
		return EXIT_SUCCESS;
	}

	/* Arrive here if I am the parent.
	Copy from the stdin to the server. */

	while((c = getchar()) != EOF) {
		char ch = c;
		if (write(s, &ch, 1) != 1) {
			perror(progname);
			return 11;
		}
	}

	if (shutdown(s, SHUT_RDWR) != 0) {
		perror(progname);
		return 12;
	}

	printf("Connection closed.\n");
	return EXIT_SUCCESS;
}

void death_of_child(int sig)
{
	int status;

	if (wait(&status) < 0) {
		perror(progname);
		exit(13);
	}

	if (!WIFEXITED(status) || WEXITSTATUS(status) != EXIT_SUCCESS) {
		fprintf(stderr, "%s: child did not return exit status %d.\n",
			progname, EXIT_SUCCESS);
	}

	if (shutdown(s, SHUT_RDWR) != 0) {
		perror(progname);
		exit(14);
	}

	printf("Connection closed by foreign host.\n");
	exit(EXIT_SUCCESS);
}