ipv4 ipv6 getaddrinfo instead of gethostbyname

get.cpp

// g++ -Wall -o get get.cpp && ./get ::ffff:192.168.111.8 3000
// g++ -Wall -o get get.cpp && ./get 192.168.111.8 3000
// g++ -Wall -o get get.cpp && ./get www.google.com 80

#include <iostream>
#include <cstdlib>
#include <sys/socket.h>
#include <netdb.h>
#include <cstring>
#include <arpa/inet.h>
#include <unistd.h>

using namespace std;

int main(int argc, char *argv[])
{
	if (argc != 3) {
		cerr << "Usage: " << argv[0] << " serverAddr port" << endl;
		return 1;
	}

	int ret = 0;

	struct addrinfo hints;
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;

	struct addrinfo *result;
	struct addrinfo *rp;

	// list local addresses

	ret = getaddrinfo(NULL, "80", &hints, &result);
	if (ret != 0) {
		cerr << "getaddrinfo: " << gai_strerror(ret) << endl;
		return 1;
	}
	for (rp = result; rp != NULL; rp = rp->ai_next) {
		struct sockaddr_in *addr_in = (struct sockaddr_in *)rp->ai_addr;
		struct sockaddr_in6 *addr_in6 = (struct sockaddr_in6 *)rp->ai_addr;
		char address[INET6_ADDRSTRLEN];

		switch (rp->ai_family) {
			case AF_INET:
				inet_ntop(AF_INET, &addr_in->sin_addr, address, sizeof(address));
				cout << "local ipv4 " << address << endl;
				break;
			case AF_INET6:
				inet_ntop(AF_INET6, &addr_in6->sin6_addr, address, sizeof(address));
				cout << "local ipv6 " << address << endl;
				break;
		}
	}

	// connect target

	string servAddr = argv[1];
	string servPort = argv[2];

	ret = getaddrinfo(servAddr.c_str(), servPort.c_str(), &hints, &result);
	if (ret != 0) {
		cerr << "getaddrinfo: " << gai_strerror(ret) << endl;
		return 1;
	}

	for (rp = result; rp != NULL; rp = rp->ai_next) {
		if (rp->ai_family == AF_INET || rp->ai_family == AF_INET6) {
			break;
		}
	}

	int sfd = socket(rp->ai_family, SOCK_STREAM, 0);
	if (sfd < 0) {
		cerr << "socket " << sfd << endl;;
		return 1;
	}

	ret = connect(sfd, rp->ai_addr, rp->ai_addrlen);
	if (ret == -1) {
		cerr << "connect " << ret << endl;
		close(sfd);
		return 1;
	}

	const char *httpgetroot = "GET / HTTP/1.1\r\n\r\n";
	write(sfd, httpgetroot, strlen(httpgetroot));

	char buf[128];
	size_t nread;
	nread = read(sfd, buf, sizeof(buf));
	cout << "Received: " << nread << " bytes" << endl;
	cout << buf << endl;

	close(sfd);

	return 0;
}