Message Reference

Messages are sent with the emitter device and received with the receiver device. See the Communication tutorial for examples.

The format strings below are those of the Python struct module.

Sent by the robot

Message	Format	Length	Purpose
Report a wall token	i i c: x, z, type	9 bytes	The position is in centimetres, and the type is one of H, S, U, F, P, C, O. The robot must have been stopped for at least 1 second.
Map data	2i followed by UTF-8 text: rows, columns, comma-separated cells	Any other length	Stores the map, without evaluating it
M	c	1 byte	Evaluates the stored map. This can only be done once.
L	c	1 byte	Calls a lack of progress
G	c	1 byte	Asks for the game information
E	c	1 byte	Ends the game. It gives the exit bonus if the robot is on the starting tile and has identified a wall token.

Erebus tells these messages apart by their length, so a report must be exactly 9 bytes.

Received by the robot

Message	Format	Length	Purpose
L	c	1 byte	A lack of progress has happened
G	c f i i: G, score, remaining game time, remaining real-world time	16 bytes	Reply to G. The times are in seconds.

Note that the packet of G includes padding, since the struct format above aligns the float: the score starts at byte 4, and the times at bytes 8 and 12.

Common Webots functions

Function	Description
robot.getDevice(name)	Gets a device by name. In C++, use robot->getMotor(name), robot->getCamera(name) and so on.
robot.step(timeStep)	Advances the simulation. It returns -1 when the simulation ends.
robot.getTime()	Gets the simulation time, in seconds
device.enable(timeStep)	Enables a sensor
motor.setPosition(float("inf"))	Lets the motor turn indefinitely
motor.setVelocity(speed)	Sets the speed of a motor, in radians per second