Obtain token for given IP address

[sedrubal]

As far as I see there is no command line option to obtain the token for a device with a specific IP address by just sending the special UDP package (21310020ff...) to port 54321 and extract the token.
Here are some hacky lines to extend the discover option, which should do the job but are not good enough for a pull request 😉:

  @cli.command()
  @click.option('--handshake', type=bool, default=False)
+ @click.option('--ip', envvar="MIROBO_IP", callback=validate_ip)
  def discover(handshake, ip):
      """Search for robots in the network."""
+     if ip:
+         vac = miio.Vacuum(ip)
+         m = vac.do_discover()
+         import binascii
+         import codecs
+         _LOGGER.info("  IP %s (ID: %s) - token: %s",
+                      ip,
+                      binascii.hexlify(m.header.value.device_id).decode(),
+                      codecs.encode(m.checksum, 'hex'))
+         return

    if handshake:
        miio.Vacuum.discover()
    else:
        miio.Discovery.discover_mdns()

P. S.: Thanks for your project.

[rytilahti]

The handshake handling could really use some cleaning up to make it also nicer for external use, there is #152 which goes towards this direction and we are open for PRs to make it happen :-)

[rytilahti]

To clean up the open issues, I'm closing this in favor of #152.