Send room temperature to heater

You can configure your heating system to take into account the room temperature when calculating the flow temperature in the same way as a room unit would do. To enable this feature for heating circuit 1, for example, you have to set parameter 750 at least to 1% (see here for the details of this value).
In order to send the room temperature to the heating system, you now can use parameter 10000 for heating circuit 1 (or 10001 and 10002 for heating circuits 2 and 3 respectively). The room temperature needs to be sent as an INF telegram and it has to be sent at least every 10 minutes, otherwise the system will fall back to outside temperature only, so you have to send this call regularly:
http://bsb-lan.local/I10000=x
where x is the room temperature you want to send.

Please take note that you must have configured BSB-LAN to be able to set/write parameters to the heating system in the configuration.
Since you cannot read from parameter 10000, you have to find the corresponding parameter in the Diagnostics / Consumer category (parameter 8740 on many heating systems).