web.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

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

int main(int argc, char** argv) {
    if (argc != 3) { /* usage */
        fprintf(stderr, "rawip hostname port\n");
        return EXIT_FAILURE;
    }

    const char* server_hostname = argv[1];
    const char* server_port = argv[2];

    struct addrinfo* addrs = NULL;
    struct addrinfo hints;
    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    int gai_res = getaddrinfo(server_hostname, server_port, &hints, &addrs);

    if (gai_res != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(gai_res));
        return EXIT_FAILURE;
    }

    if (addrs == NULL) {
        fprintf(stderr, "No available host interfaces\n");
        return EXIT_FAILURE;
    }

    int sockfd = socket(
        addrs[0].ai_family,
        addrs[0].ai_socktype,
        addrs[0].ai_protocol
    );

    if (sockfd == -1) {
        perror("socket");
        freeaddrinfo(addrs);
        return EXIT_FAILURE;
    }

    int conn_res = connect(sockfd, addrs[0].ai_addr, addrs[0].ai_addrlen);

    if (conn_res == -1) {
        perror("connect");
        freeaddrinfo(addrs);
        return EXIT_FAILURE;
    }

    const char* msg = "Hello, world!";
    size_t msglen = strlen(msg) + 1;
    int bytes_sent = send(sockfd, msg, msglen, 0);

    uint8_t* resp = calloc(1024, sizeof(uint8_t));
    size_t resplen = 1024;
    int bytes_received = recv(sockfd, resp, resplen, 0);

    printf("%s\n", resp);

    freeaddrinfo(addrs);

    free(resp);

    return EXIT_SUCCESS;
}