Two services

# users_service.py

from isc.server import Node, expose, on
from superapp.models import User

class UserService(object):
    name = 'users'

    @expose
    def get_user(self, id):
        # Let's use some ORM to retrieve the user from DB
        user = User.objects.filter(id=id).first()
        if user:
            # User not found!
            return {'username': user.username}
        return None

    @on('new_message')
    def on_new_message(self, username, message):
        print('New message for user {}: {}'.format(username, message))

node = Node()
node.register_service(UserService())
try:
    node.run()
except KeyboardInterrupt:
    node.stop()

# messages_service.py

from isc.server import Node, expose
from isc.client import Client
from superapp.models import Message

client = Client()

class MessageService(object):
    name = 'messages'

    @expose
    def send_message(self, body, receipt):
        user = client.users.get_user(receipt)
        if not user:
            # User not found!
            raise Exception('Cannot send message: user not found')
        Message.objects.create(receipt=receipt, message=body)

        # Broadcast to all instances
        client.notify('new_message', user['username'], message)

node = Node()
node.register_service(MessageService())
try:
    node.run()
except KeyboardInterrupt:
    node.stop()

# app.py

from isc.client import Client

client = Client()

# ...

try:
    client.messages.send_message('Hello!', some_user_id)
except RemoteException as e:
    print('Failed to send message, error was: {}'.format(str(e)))
else:
    print('Message send!')