function sendKeepAliveCommand() {
    var navSock = sockets['nav'];
    if (!SIMULATE) {
      try {
        chrome.sockets.udp.send(
          navSock.socket,
          (new Uint8Array([1])).buffer,
          DRONE_IP,
          navSock.port,
          function(sendInfo) {
            if (sendInfo.resultCode < 0) {
              shutdown();
            }
          });
      } catch(err) {
        shutdown();
      }

    }

    // set up a keepalive because The drone does not receive any traffic for more than 2000ms;
    // it will then stop all communication with the client
    if (keepAliveTimeout) clearTimeout(keepAliveTimeout);
    keepAliveTimeout = setTimeout(sendKeepAliveCommand, 1000);
  }
Sends a keepalive command and attempts to read
back the latest data from the drone