tcp-ip-sockets-in-c/ch3/TCPClientUtility.c

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>

#include "Practical.h"

int setup_tcp_client_socket(const char *host, const char *service) {
    struct addrinfo addr_criteria = {0};
    addr_criteria.ai_family = AF_UNSPEC;
    addr_criteria.ai_socktype = SOCK_STREAM;
    addr_criteria.ai_protocol = proto_get_num("tcp");

    struct addrinfo *serv_addr = nullptr;
    int ret = getaddrinfo(host, service, &addr_criteria, &serv_addr);
    if (ret != 0) {
        DieWithUserMessage("getaddrinfo() failed", gai_strerror(ret));
    }

    int sock = -1;
    for (struct addrinfo *addr = serv_addr; addr != nullptr; addr = addr->ai_next) {
        sock = socket(AF_to_PF(addr->ai_family), addr->ai_socktype, addr->ai_protocol);
        if (sock < 0) {
            continue;
        }

        ret = connect(sock, addr->ai_addr, addr->ai_addrlen);
        if (ret == 0) {
            break;
        } else {
            close(sock);
            sock = -1;
        }
    }

    freeaddrinfo(serv_addr);

    return sock;
}