Understanding htonl() and ntohl()
<p>I am trying to use unix sockets to test sending some udp packets to localhost.</p>

<p>It is my understanding that when setting ip address and port in order to send packets, I would fill my <code>sockaddr_in</code>with values converted to network-byte order.
I am on OSX and I'm astonished that this</p>

<pre><code>printf("ntohl: %d\n", ntohl(4711));
printf("htonl: %d\n", htonl(4711));
printf("plain: %d\n", 4711);
</code></pre>

<p>Prints</p>

<pre><code>ntohl: 1729232896
htonl: 1729232896
plain: 4711
</code></pre>

<p>So  neither function actually returns the plain value. I would have expected to see either the results differ, as x86 is little-endian (afaik), or be identical and the same as the actual number 4711. Clearly I do not understand what <code>htonl</code> and <code>ntohl</code> and their variants do. What am I missing?</p>

<p>The relevant code is this:</p>

<pre><code>int main(int argc, char *argv[])
{
   if (argc != 4)
   {
      fprintf(stderr, "%s\n", HELP);
      exit(-1);
   }

   in_addr_t rec_addr = inet_addr(argv[1]); // first arg is '127.0.0.1'
   in_port_t rec_port = atoi(argv[2]);      // second arg is port number
   printf("Address is %s\nPort is %d\n", argv[1], rec_port);
   char* inpath = argv[3];

   char* file_buf;
   unsigned long file_size = readFile(inpath, &amp;file_buf); // I am trying to send a file
   if (file_size &gt; 0)
   {
      struct sockaddr_in dest;
      dest.sin_family      = AF_INET;
      dest.sin_addr.s_addr = rec_addr; // here I would use htons
      dest.sin_port        = rec_port;
      printf("ntohs: %d\n", ntohl(4711));
      printf("htons: %d\n", htonl(4711));
      printf("plain: %d\n", 4711);
      int socket_fd = socket(AF_INET, SOCK_DGRAM, 0);
      if (socket_fd != -1)
      {
         int error;
         error = sendto(socket_fd, file_buf, file_size + 1, 0, (struct sockaddr*)&amp;dest, sizeof(dest));
         if (error == -1)
            fprintf(stderr, "%s\n", strerror(errno));
         else printf("Sent %d bytes.\n", error);
      }
   }

   free(file_buf);
   return 0;
}
</code></pre>