Called when asyncio.Protocol establishes the network connection.

def connection_made(self, transport):
        """Called when asyncio.Protocol establishes the network connection."""
        self.log.info('Connection established to AVR')
        self.transport = transport

        #self.transport.set_write_buffer_limits(0)
        limit_low, limit_high = self.transport.get_write_buffer_limits()
        self.log.debug('Write buffer limits %d to %d', limit_low, limit_high)

        self.command('ECH1')
        self.refresh_core()