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

char *progname;


void
usage(void)
{
	fprintf(stderr, "Usage: %s USER@HOST [PORT]\n", progname);
	exit(1);
}


int
main(int argc, char** argv)
{
	char *cp, *host = "localhost", *user;
	short port = 79;

	progname = argv[0];
	if (argc == 1 || argc > 3) {
		usage();
	}
	if (argc >= 2) {
		user = argv[1];
		if ((cp = strchr(user, '@'))) {
			*cp = '\0';
			host = cp + 1;
		}
	}
	if (argc == 3) {
		port = atoi(argv[2]);
		if (port < 1) {
			fprintf(stderr, "port number must be positive");
			exit(1);
		}
	}

	struct hostent* hp;
	if ((hp = gethostbyname(host)) == 0) {
		fprintf(stderr, "unknown host: %s\n", host);
		exit(1);
	}

	char* hostaddr = hp->h_addr_list[0];
	struct sockaddr_in addr = {0};
	addr.sin_family = AF_INET;
	memmove((void *)&addr.sin_addr, (void *)hostaddr, hp->h_length);
	addr.sin_port = htons(port);


	int fd;
	if ((fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}
	if (connect(fd, (struct sockaddr *) &addr, sizeof addr) == -1) {
		perror("connect");
		exit(1);
	}

	write(fd, user, strlen(user));
	write(fd, "\r\n", 2);

	char buf[BUFSIZ];
	ssize_t nbytes;
	while((nbytes = read(fd, buf, sizeof buf)) > 0 &&
			write(1, buf, nbytes) == nbytes) {
		;
	}
}