The invention relates to a method for data communication in a communication system, comprising a plurality of communication participants, each participant having a subsystem responsible for communication, whereby a communication participant acts as master (1) of the communication system, the subsystem of the master being operated continuously, whereby the other communication participants act as communication slaves (5) in the communication system, the subsystems of the communication slaves (5) being de-energized, when no communication takes place. Further, a protocol for controlling a bidirectional communication is provided, whereby establishment of the communication results from a special initial packet, which is transmitted by a communication slave (5) to a communication master (1); the initial packet is acknowledged by the master (1) with a confirmation packet; and this confirmation packet comprises information, whether subsequent communication is required. Moreover, a communication system is provided, comprising a plurality of communication participants (1, 5), each having a respective subsystem responsible for the communication, whereby at least one communication participant is adapted to act as master (1) in the communication system, having a continuously operating subsystem, whereby the other communication participants are adapted to act as communication slaves (5) in the communication system, having subsystems, which are de-energized, when no communication takes place, whereby the communication participants are sensors (4).