Protocol

UDPWiiHook uses a extended version of Dolphin's UDPWii protocol, which is backward compatible with the original. Here documents both protocols, for a easier future reference.

Consult cemuhook-protocol for DSU/Cemuhook-side protocols.

General notes

• The most relible UDPWii doc I could find is a random post on Dolphin Forums, which unfortunately also contains errors when compared with actual Dolphin source code. Helpful still, kudos to da_petcu21.
• Data types use a C#-like naming convention: Bytes are unsigned, IntNN/UIntNN means signed/unsigned NN-bit integer, [Flags] marks a bitfield.
• Any multi-byte integer in a UDPWii packet is in network byte order, which is different from most common platforms.
• Floats are actually 32-bit signed integers (Int32s) - they are scaled by a factor of 1024 * 1024 and kept only the integral part.
• UDPWiiHook extensions are highlighted with a italic font.

Data packet

After each given interval (33ms in case of UDPMote), a Data packet is sent from UDPWii apps to Dolphin.

Header

Exists in every Data packet.

Offset	Length	Type	Description
0	1	Byte	Signature; should be 0xde
1	1	[Flags] Byte	Header flags; mark which data chunks exist in this packet
2	?	?	Data chunks

Header flags

NOTE: Data chunks are ordered by their bit offset, with no padding bytes in place of a missing chunk.

Bit No.	Value	Description
0	1	Acceleration
1	2	Buttons
2	4	IR
3	8	Nunchuk
4	16	Nunchuk Acceleration
5	32	Acceleration Timestamp
6	64	Gyroscope

Acceleration data chunk

Accelerometer readings are in Gs.

Offset	Length	Type	Description
0	4	Float	Accelerometer X axis
4	4	Float	Accelerometer Y axis
8	4	Float	Accelerometer Z axis
12	-	-	Data chunk ends

Buttons data chunk

The whole Buttons data chunk is a unsigned 32-bit bitfield ([Flags] UInt32, 4 bytes). Definitions for each bit are as follows.

Bit No.	Value	Description
0	1	Key 1
1	2	Key 2
2	4	Key A
3	8	Key B
4	16	Key +
5	32	Key -
6	64	Key Home
7	128	Key Up
8	256	Key Down
9	512	Key Left
10	1024	Key Right
11	2048	Key "SK" (Sync button?)

IR data chunk

IR coordinates in a UDPWii packet has its origin at the bottom-left corner of the screen, with (1.0, 1.0) at the top-right corner.

These coordinates are absloute; meaning that they just tell the current position Wiimote is pointing at, no fancy delta calculations.

Offset	Length	Type	Description
0	4	Float	IR X position
4	4	Float	IR Y position
8	-	-	Data chunk ends

Nunchuk data chunk

Unused in most UDPWii apps and UDPWiiHook.

Offset	Length	Type	Description
0	1	[Flags] Byte	Nunchuk buttons
1	4	Float	Analog stick X position
5	4	Float	Analog stick Y position
9	-	-	Data chunk ends

Nunchuk buttons

Bit No.	Value	Description
0	1	Key C
1	2	Key Z

Nunchuk Acceleration data chunk

Unused in most UDPWii apps and UDPWiiHook.

Accelerometer readings are in Gs.

Offset	Length	Type	Description
0	4	Float	Accelerometer X axis
4	4	Float	Accelerometer Y axis
8	4	Float	Accelerometer Z axis
12	-	-	Data chunk ends

Acceleration Timestamp data chunk

The whole Acceleration Timestamp data chunk is a unsigned 64-bit integer (UInt64, 8 bytes), in nanoseconds.

Gyroscope data chunk

Gyroscope readings are in radians per second.

Offset	Length	Type	Description
0	4	Float	Gyroscope pitch
4	4	Float	Gyroscope yaw
8	4	Float	Gyroscope roll
12	-	-	Data chunk ends

Broadcast packet

A Broadcast packet is sent periodically for each free Wiimote slot by Dolphin to 255.255.255.255 to announce it's presence.

Offset	Length	Type	Description
0	1	Byte	Signature; should be 0xdf
1	2	UInt16	Random numbers; should be unique per-Wiimote
3	1	Byte	Slot number (0-3)
4	2	UInt16	UDP port number for clients to send Data packets to
6	1	Byte	Length of the display name
7	?	Byte[]	The display name; length given above