title: Generate a random byte stream
body: <p>I'm testing a network program that sends packet to a remote server using UDP/TCP, and for that,
  I want to generate some random byte streams.</p>
  
  <p>Here's the function:</p>
  
  <pre><code>unsigned char *gen_rdm_bytestream(int num_bytes)
  {
      unsigned char *stream = malloc(num_bytes);
      /*
       * here how to generate?
       */
      return stream;
  }
  </code></pre>