Hello Peter,
your RPC seems fine, so I believe you are using netopeer-server and not netopeer-server-sl? Toaster is an example transAPI module included in the single-layer (sl) server, but this one is no longer supported. However, there is an example module in the multi-level server as well and you can find it in "netopeer/transAPI/turing", it's a Turing machine simulation. I suggest you play with that module, installing it will also add it to the netopeer-server.
There is also the possibility of adding the toaster module into netopeer-server, but it requires some basic knowledge of the server and modules, which I'm not sure you have. But it is quite simple, you can do it with the help of the netopeer-manager utility. Also, using netopeer-configurator you can see all the installed transAPI modules and other useful information.
Regards,
Michal