CIG 2007 Car Racing Competition

TCP Communications protocol

The protocol for client-server communication was designed to be as simple as possible. In fact, it is so simple it's hardly even a protocol...

First of all, the client connects via TCP to the server, locally or remotely. The port number depends on how the server was started. The class TCPControllerOne listens on port 6524, and TCPControllerTwo on 6525. (Other than that, there is no difference at all between the two classes, and you can use whichever you want to control a single car. There are two of them just to make it easier to control two cars with different controllers over TCP.)

What happens then is that each time step (there are 500 time steps to a trial) the server sends the current state of the car and its environment, and the client responds with the action to take. The one exception is at the beginning of each trial (episode), when the server sends a message consisting only of the word "reset"; the client is not supposed to answer to this, but is supposed to clear its internal state if it has any, as the way points are re-randomized and the car(s) re-positioned.

The state information consists of an ascii string terminated with a line break, beginning with the word "data" followed by a space, and then followed by 22 space-separated fields. The first of these fields has the value "true" if there is another car on the arena, and the value "false" otherwise. The other 21 fields are all double-precision ascii-encoded real numbers, e.g. "0.25657235" and "2.5644562". Their ordering and approximate ranges are as follows:

speed	0..5
angle to current waypoint	-pi..pi
distance to current waypoint	0..400
angle to next waypoint	-pi..pi
distance to next waypoint	0..400
angle to other car	-pi..pi
distance to other car	0..400
own position (x)	0..400
own position (y)	0..400
own velocity (x)	0..5
own velocity (y)	0..5
own orientation	-pi..pi
other car's position (x)	0..400
other car's position (y)	0..400
other car's velocity (x)	0..5
other car's velocity (y)	0..5
other car's orientation	-pi..pi
current waypoint's position (x)	0..400
current waypoint's position (y)	0..400
next waypoint's position (x)	0..400
next waypoint's position (y)	0..400

Of these fields, the first seven can be classified as first-person, or local frame of reference, information. Conversely, the last fourteen are better seen as third-person, or global frame of reference, information. Experience has shown that using first-person data is usually strongly advisable when constructing your controller; however, the third-person data is more complete and is included here for those that want to do their own coordinate transformations and/or construct complicated models (e.g. of the dynamics of the own car and behaviour of the other car).