title: Connect two raspberry Pis using USB cable or USB-serial
body: <p>I'm working on a project where I need two raspberry pis to communicate and the ethernet port is not free, I'm not allowed to make any changes to the GPIO pins, and I'm forced to use the USB port due to hardware considerations. Is it possible for them to communicate using a direct USB cable, or perhaps using two USB-RS232 cables?</p>
  
  <p>Thanks!</p>
  
  <p>Siddharth</p>