Sorry for the long wait, we had a DNS change and this took us sometime.
This is totally possible.
Streamsheets comes with the Mosquitto broker preinstalled, so you can use it locally.
We use docker as the environment to run everything in.
If I understand you correctly, you will need an HTTP Server to interact with.Streamsheets can be a HTTP Server, but this is a premium feature. If you already have a Server to send your commands to, Streamsheet could interact with this server and build the bridge between HTTP/REST data and MQTT data.
Here we show how to use HTTP/REST:
Here we show how to connect to an MQTT Stream:
And here how to work with Inbox messages:
If you connect all these 3 together you should be able to manage your Use Case
Have fun and let me know if you have any further questions.