Player interaction

The player is moving in either horizontal or vertical direction. Those moves are sent to the server as an OP_MOVE message. A player can set up a bomb somewhere, in which case the server will receive an OP_ACTION message. Both messages are broadcasted to all players by the server, whereas more might be sent out (with different meanings) by the server itself. This is what the server-side OP_MOVE and OP_ACTION are for.