tests/sockets/test_gethostbyname.c

#include <arpa/inet.h>
#include <sys/socket.h>
#include <assert.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#endif

int main() {
  char str[INET_ADDRSTRLEN];
  struct hostent *host = NULL;
  struct hostent hostData;
  struct in_addr addr;
  const char *res;
  char buffer[2048];
  int err;
  
  // gethostbyname_r calls the same stuff as gethostbyname, so we'll test the
  // more complicated one.
  // resolve the hostname to an actual address
  gethostbyname_r("slashdot.org", &hostData, buffer, sizeof(buffer), &host, &err);
  assert(host->h_addrtype == AF_INET);
  assert(host->h_length == sizeof(uint32_t));

  // convert the raw address to a string
  char **raw_addr_list = host->h_addr_list;
  int *raw_addr = (int*)*raw_addr_list;
  res = inet_ntop(host->h_addrtype, raw_addr, str, INET_ADDRSTRLEN);
  assert(res);

  // convert the string to an in_addr structure
  err = inet_pton(AF_INET, str, &addr);
  assert(err == 1);

  // do a reverse lookup on the ip address
  struct hostent *host1 = gethostbyaddr(&addr, sizeof(addr), host->h_addrtype);
  assert(strstr(host1->h_name, "slashdot.org"));

  puts("success");

  return EXIT_SUCCESS;
}