UDP communication protocol
--------------------------

Clients "connect" by sending any UDP packet to port 4791.  The packet need
not contain a valid command.  Once connected, the server will send status
packets.  The connection remains active for 60 seconds, and any UDP packet
to port 4791 renews the 60 second timeout.

The status packets are transmitted at a regular rate, typically 50 per
second.  The format of the status packet is:

bytes 0 to 31: current motor position, 0 to 95
bytes 32 to 63: current motor status, 0=motor disabled, 1=motor enabled
bytes 64 to 69: current sonar reading, 0 to 223, distance in half inches

Additional bytes may be added with more status information, so code
should be designed to handle larger packets and ignore the extra data


The UDP packets sent to the server may contain a command.

Enable Motor:
	byte 0: 0x7A
	byte 1: motor number, 0 to 31

Disable Motor:
	byte 0: 0x19
	byte 1: motor number, 0 to 31

Set Speed:
	byte 0: 0x45
	byte 1: motor number, 0 to 31
	byte 2: speed, -63 to +63 (signed char)

Set Motor Auto-Enable Timeout:
	byte 0: 0x6B
	byte 1: motor number, 0 to 31
	byte 2: inactivity time, 1 to 255 seconds, 0=never auto enable

Set LED:
	byte 0: 0x9C
	byte 1: board number, 0 to 7
	byte 2: LED byte, 8 LEDs

Set Position:  (not implemented yet)



Motors always disable automatically when a user touches the wheel.
The auto-enable timeout should be used to reenable the motor after a
period of inactivity (no motion from manual movement).  The motor can
also be enabled with an explict command.  However, if a user is moving
the wheel manually, it will auto-disable almost instantly.

Speed set commands to disabled motors are ignored.