1. Run touch_remote_service.sh
2. Run pairing_server.py
3. Run iTunes, find the remote device, and enter any 4-digit PIN
4. After iTunes successfully pairs with the device, run ./dacp_send.sh "login?pairing-guid=0x0000000000000001". That will return something like:

 mlog  --+                                
        mstt   4      000000c8 == 200     
        mlid   4      033c16bb == 54269627

Here, 54269627 is your session ID. Include it in all future requests.

Now you can send commands to iTunes. For example, to make iTunes pause playback:

./dacp_send.sh "ctrl-int/1/playpause?session-id=YOUR_SESSION_ID"

For more commands, see here: http://dacp.jsharkey.org/