code: private STUNService bestSTUNServer(ArrayList<STUNService> listServers) {
          if (listServers.isEmpty()) {
              return null;
          } else {
              // TODO: this should use some more advanced criteria...
              return listServers.get(0);
          }
      }
docs: Get the best usable STUN server from a list.
  
  @return the best STUN server that can be used.