Chess Engine Communication Protocol

CECP stands for Chess Engine Communication Protocol. It is also called the XBoard or WinBoard protocol because it developed around those interfaces. It lets a graphical interface send commands to a chess engine and receive moves, search information, and game results.

Communication uses text lines. The interface can send new to begin a game, force to stop the engine from playing either side, go to make it play the side to move, time and otim to report the clocks, and ping to confirm that earlier commands have been processed. Moves can use coordinate notation and, when the relevant capability is negotiated, standard algebraic notation.

Capability negotiation

In protocol version 2, the interface sends xboard and protover 2. The engine answers with one or more feature lines declaring support for items such as direct position setup, variants, configurable options, or endgame tables. The interface accepts or rejects each feature. This mechanism preserves compatibility with older engines.

CECP and UCI serve similar purposes but structure the conversation differently. CECP commonly treats the engine as a player that keeps the game state; UCI normally sends the position again before each search. Tools such as PolyGlot can adapt some UCI engines to CECP interfaces.