Query Mechanism

The backbone of packets

Byte	PHP	Hexadecimal	Description
0-3	"MP04"	4D 50 30 34	The magic of the packet.
4	chr('192');	C0	The first byte in the server's IP address.
5	chr('168');	A8	The second byte in the server's IP address.
6	chr('200');	C8	The third byte in the server's IP address.
7	chr('103');	67	The fourth byte in the server's IP address.
8	chr('5192' & 0xFF);	48	The first byte of the port.
9	chr('5192' >> 8 & 0xFF);	14	The second byte of the port.
10	"i"	69	The opcode that you would like to query.

Opcodes

The packet table

Packet 'opcode'	Description
i	Server information
p	Ping
c	Players list

Recieving the packets

The header of the query response will be the exact same thing that the client sent, except that the header sent by the server will always be MP04, and not VCMP. This acts as a compatibility check due to the differing protocols.

Response from i

Byte	Key	Byte width	Description
11-22	Version name	12	The version name of the server.
23	Password	1	A flag indicating if the server is locked, an integer that is 0 or 1.
24-25	Players	2	The number of players.
26-27	MaxPlayers	2	The maximum number of players.
Extra data (500 bytes)
28-31	strlen	4	Size of the server name.
32+strlen	Server name	strlen	The server name.
33-36	strlen	4	Size of the gamemode name.
37+strlen	Gamemode	strlen	The gamemode name.
38-41	strlen	4	Size of the map name.
42+strlen	Map name	strlen	The map name.

Anything thereafter should be treated as garbage.

Response from c

Byte	Key	Byte width	Description
11-12	Players Online	2	Number of players online.
Extra data (3000 bytes)
13-14	strlen	1	Size of player name.
Player name	14+strlen	strlen	The player name.
(repeat for however many players there are online)

Anything thereafter should be treated as garbage. Note that scores are no longer included.

Response from p

The response to a ping packet has the same structure as before, with the modified magic.

Example Implementations

PHP

Here is a PHP class written by stormeus which implements the query protocol rather strictly: http://pastie.org/9501000