MK8 Network Protocol

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This page describes the network protocol used by Mario Kart 8. It is very incomplete at this moment.

General description

The Mario Kart 8 traffic starts with a name resolution. The loginserver ( has multiple IP addresses with a TTL of 60:


and maybe some more

First the game connects the Nintendoservers, while racing, all WiiUs communicate directly to each other.

All P2P packets have a header, a payload and a checksum

The P2P headers

There are two different headers: One header at the beginning of each packet ...

typedef struct udp_main_header_t
  /*00*/   u32		game_magic;	// always 32ab.9864
  /*04*/   u32		unknown_04;	// ?
  /*08*/   u16		timer;		// Timer. Increases each 1/100 sec.
__attribute__ ((packed)) udp_main_header_t;

... and one at the beginning of each record. A packet may contain multiple records.

typedef struct udp_sub_header_t
  /*0a*/   u16		unknown_0a;	// sequence id 2 or empty
  /*0c*/   u16		unknown_0c; 	// maybe client slot (0 to b), if unknown_0a not empty?
  /*0e*/   u16		data_length; 	// little endian, data length without headers and checksum
  /*10*/   u32		receiver_slots;	// Used slot bitmask of receiver (one or two bits set)
                                        // 0x0001 -> slot 0; 0x0200 -> slot 9; 0x0000 -> no slot assigned
  /*14*/   u32		sender_pid; 	// profile ID / any unique ID of sender
  /*18*/   u32		unknown_18; 	// ?
  /*1c*/   u32		unknown_1c; 	// always 0x00000000
__attribute__ ((packed)) udp_sub_header_t;

After the main header there may follow one or more sub headers including data, after all records there is a 16-byte-checksum which looks like a MD5 hash.

Record types