twisted autobahn websocket: class for SerialPort can't inherit class method to fire sendMessage

Question

Goal is to send serial "payload" to a non-local server (static IP) using a websocket and fired each time there's new serial data from a serial device connected to a local machine (where this code runs). The following code does receive serial data...and it creates a websocket with the remote server. I can't trigger a sendmessage from the SerialDevice Class, as it breaks when I uncomment the line in class SerialDevice "BroadcastClientProtocol().sendPayload(payload)"

Here is the unhandled error: [...] if self.state != WebSocketProtocol.STATE_OPEN: exceptions.AttributeError:BroadcastClientProtocol instance has no attribute 'state'

From within SerialDevice Class, I can call a test inherited method BroadcastClientProtocol().testInheritanceMethod().

Here's the code adapted from autobahn websocket/broadcast client.py

from twisted.internet import reactor
from autobahn.twisted.websocket import WebSocketClientFactory, \
                                       WebSocketClientProtocol, \
                                       connectWS
from twisted.internet.serialport import SerialPort
from twisted.protocols.basic import LineReceiver

COM_PORT='/dev/ttyUSB0'
BAUD_RATE=115200

import sys
from twisted.internet import reactor
from autobahn.twisted.websocket import WebSocketClientFactory, \
                                       WebSocketClientProtocol, \
                                       connectWS
from twisted.internet.serialport import SerialPort
from twisted.protocols.basic import LineReceiver

COM_PORT='/dev/ttyUSB0'
BAUD_RATE=115200

class SerialDevice(LineReceiver):
     def __init__(self, network):
         pass

     def lineReceived(self, payload):
         print "receive:", payload
         #the call to the inherited method testInheritanceMethod() works
         BroadcastClientProtocol().testInheritanceMethod()

         #the call to the inherited method sendPayload() fails
         #BroadcastClientProtocol().sendPayload(payload)

class BroadcastClientProtocol(WebSocketClientProtocol):
   """
   Simple client that connects to a WebSocket server, send a HELLO
   message every 2 seconds and print everything it receives.
   """
   def testInheritanceMethod(self):
      print("inherited method called OK")

   def sendHello(self):
      self.sendMessage("Hello from Python!".encode('utf8'))
      reactor.callLater(2, self.sendHello)

   def sendPayload(self, data):
      self.sendMessage(data.encode('utf8'))

   def onOpen(self):
      self.sendHello()

   def onMessage(self, payload, isBinary):
      if not isBinary:
         print("Text message received: {}".format(payload.decode('utf8')))


if __name__ == '__main__':

   if len(sys.argv) < 2:
      print("Need the WebSocket server address, i.e. ws://localhost:9000")
      sys.exit(1)

   factory = WebSocketClientFactory(sys.argv[1])
   factory.protocol = BroadcastClientProtocol
   connectWS(factory)
   SerialPort(SerialDevice(BroadcastClientProtocol), COM_PORT, reactor, baudrate=BAUD_RATE)

   reactor.run()