Twisted Python + Spawnprocess. Getting Output From A Command

I'm working to wrap the Minecraft server application with a Twisted Python server that has a RESTful API for getting the list of currently connected players. The Twisted app starts

Solution 1:

First, do not call writeSomeData ever. Call write. Second, having a global protocol instance is probably a bad idea, for all the usual reasons globals are generally a bad idea.

Third, add a method to the ProcessProtocol subclass for getting the information you want. The protocol's job is knowing how to turn abstract actions, like "ask for a list of players" into byte sequences to transmit and how to turn received byte sequences back into abstract actions like "the process told me these players are connected".

classNotchianProcessProtocol(protocol.ProcessProtocol):
    ...
    deflistPlayers(self):
        self.transport.write("list")
        self._waiting.append(Deferred())
        return self._waiting[-1]

    defoutReceived(self, bytes):
        outbuffer = self.outbuffer + bytes
        lines, leftover = parseLines(outbuffer)
        self.outbuffer = leftover

        for line in lines:
            if line.startswith('[INFO] Connected players: '):
                self._waiting.pop(0).callback(line)

Now any of your code which has a reference to a connected NotchianProcessProtocol can call listPlayers on it and get back a Deferred which will fire with connected player information shortly afterwards.