test_204.c

test_204.c

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

#define BUF_SIZE 1024

int main(int argc, char *argv[]) {
  const char hostname[] = "www.gstatic.com";
  const char port[] = "80";
  const char request[] = "GET /generate_204 HTTP/1.1\r\n"
                         "Host: www.gstatic.com\r\n"
                         "Accept: */*\r\n"
                         "Connection: close\r\n"
                         "\r\n";
  const size_t len = sizeof(request) - 1;
  const char http_1_1[] = "HTTP/1.1";
  const size_t http_1_1_len = sizeof(http_1_1) - 1;
  char buf[BUF_SIZE];
  ssize_t nread;
  int sfd, s;
  struct addrinfo *result, *rp;
  struct addrinfo hints = {
      .ai_family = AF_UNSPEC,
      .ai_socktype = SOCK_STREAM,
      .ai_flags = AI_V4MAPPED | AI_ADDRCONFIG,
      .ai_protocol = 0,
  };

  s = getaddrinfo(hostname, port, &hints, &result);
  if (s != 0) {
    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
    return EXIT_FAILURE;
  }

  for (rp = result; rp != NULL; rp = rp->ai_next) {
    sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
    if (sfd == -1)
      continue;

    if (connect(sfd, rp->ai_addr, rp->ai_addrlen) != -1)
      break; /* Success */

    close(sfd);
  }

  freeaddrinfo(result); /* No longer needed */

  if (rp == NULL) { /* No address succeeded */
    fprintf(stderr, "Could not connect\n");
    return EXIT_FAILURE;
  }
  if (write(sfd, request, len) != len) {
    fprintf(stderr, "partial/failed write\n");
    return EXIT_FAILURE;
  }
  if (shutdown(sfd, SHUT_WR) != 0) {
    perror("shutdown");
    return EXIT_FAILURE;
  }
  nread = read(sfd, buf, BUF_SIZE);
  if (nread == -1) {
    perror("read");
    return EXIT_FAILURE;
  }
  if (nread < 12 || strncmp(buf, http_1_1, http_1_1_len) != 0) {
    fprintf(stderr, "bad http response");
    return EXIT_FAILURE;
  }
  const char *status = buf + 9;
  if (status[0] != '2' || status[1] != '0' || status[2] != '4') {
    fprintf(stderr, "http status: %.3s\n", status);
    return EXIT_FAILURE;
  }
  while (nread != 0 && nread == -1) {
    nread = read(sfd, buf, BUF_SIZE);
  }
  return EXIT_SUCCESS;
}