talker.c

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

#define SERVERPORT "4950"

int main(int argc, char* argv[])
{
	if(argc != 3) {
		fprintf(stderr, "usage: <hostname> <message>\n");
		exit(1);
	}

	struct addrinfo hints;
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_INET6;
	hints.ai_socktype = SOCK_DGRAM;
	
	struct addrinfo* servinfo;
	int gai_res = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo);
	if(gai_res != 0) {
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(gai_res));
		exit(1);
	}

	int sockfd;
	struct addrinfo* p;
	for(p = servinfo; p != NULL; p = p->ai_next) {
		sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
		if(sockfd == -1) {
			perror("talker: socket");
			continue;
		}

		break;
	}

	if(p == NULL) {
		fprintf(stderr, "talker: failed to create socket\n");
		exit(1);
	}

	int num_bytes = sendto(sockfd, argv[2], strlen(argv[2]), 0, p->ai_addr, p->ai_addrlen);
	if(num_bytes == -1) {
		perror("talker: sendto");
		exit(1);
	}

	freeaddrinfo(servinfo);

	printf("talker: sent %d bytes to %s\n", num_bytes, argv[1]);

	close(sockfd);

	exit(0);
}