codice:
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

void inet_all (struct sockaddr_in *data, int port, long int ip);

int main (void) {
	int sock;
	struct sockaddr_in info;
	inet_all(&info, 6669, inet_addr("pierotofy1.no-ip.org"));
	sock = socket(AF_INET, SOCK_STREAM, 0);
	if (sock < 0) {
		puts("Error to created a socket");
		exit(EXIT_FAILURE);
	}
	if (connect(sock, (struct sockaddr *) &info, sizeof(struct sockaddr)) < 0) {
		puts("Error to connected at the server");
		exit(EXIT_FAILURE);
	}
	close(sock);
	return 0;
}

void inet_all (struct sockaddr_in *data, int port, long int ip) {
	data->sin_family = AF_INET;
	data->sin_port = htons(port);
	data->sin_addr.s_addr = ip;
	return;
}
Dove sbaglio?