The invention relates to a method for transmitting messages in a computer network of a real-time system comprising components in the form of computing nodes and star couplets. A first group of components sends, relays or receives time-controlled messages according to a communication schedule, and a second group of components does not communicate according to a communication schedule. For example, the computing node 104 does not execute a communication schedule, i.e. the computing node 104 does not send time-controlled messages. Instead, the computing node 104 reacts to receiving a message 1-201a by sending a message 1-104a in response. According to the invention, the message 1-201a is sent in a time-controlled manner, for example by a star coupler 201. The computing node 104 receives the message 1-201a at time 17-104a and reacts to receiving the message 1-201a by sending the message 1-104a at time 17-104b to the star coupler 201. The star coupler 201 receives the message 1-104a at time 14-201b. Preferably an upper limit OBS of the maximum time interval between the receiving time 17-104a and the sending time 17-104b is determined in the computing node 104. In this way, the star coupler 201 can schedule the relaying time 14-201c, at which the message 1-104a is relayed in the network, as a time-controlled time. Alternatively, the computing node 104 reacts by reading a current value from a local sensor, by altering the state of an actuator.