Interacting with RPC devices via device files.

[blackdragon2447]

I've recently been looking into interacting with RPC devices via devices files, from looking through the devices.py script i was able to decipher that the /dev/hvc0 file is used to do so, and that this communication is done via jsons separated by null characters, source:

def _write_message(self, data):
    self.file.write(self.MESSAGE_DELIMITER + json.dumps(data) + self.MESSAGE_DELIMITER)

so writing [[null]]{"type": "list"}[[null]] into the file and than reading the file (using something like cat) should return a json containing a list of all the devices (wrapped in null characters), for how far is this correct (since I cant seem to read anything from the file)?
As for calling methods on devices via this method, do the arguments for the method need to be a json objet:

{
    "type": "invoke",
    "data": {
        "deviceId": 0,
        "name": "getRedstoneInput",
        "parameters": {
            "side": "west"
        }
    }
}

or a list:

{
    "type": "invoke",
    "data": {
        "deviceId": 0,
        "name": "getRedstoneInput",
        "parameters": [
            "west"
        ]
    }
}

and does the order of the fields on the json matter?

[sannelo]

I'm not entirely sure I understand you.
My friend created a library for c/cpp which just interacts with devices.
https://github.com/Bs0Dd/Coverett

[blackdragon2447]

looking at the library it seems to be doing about the same as what i am doing to for some reason my code (rust) refuses to properly write to the device file.

[fnuecke]

Yes, that is the basic format of the RPC "protocol". One tricky bit is the need to switch the hvc0 into raw mode after opening it (as seen here). The parameters field is a list/array, in the order the backing RPC method expects them, so order does matter.