Volttron throws an Attribute error when attempting to publish - volttron

Question

I am combining Scapy with Volttron and I want to publish to a topic when a packet comes in and has certain features. However, I keep running into this error:
Traceback (most recent call last): File "sniff.py", line 373, in
sys.exit(main()) File "sniff.py", line 342, in main
utils.vip_main(sniffer, version=version) File "/home/jenny/workspace/volttron/volttron/platform/agent/utils.py",
line 314, in vip_main
version=version, **kwargs) File "sniff.py", line 336, in sniffer
Sniffer(**kwargs) File "sniff.py", line 138, in init
self.vip.pubsub.publish('pubsub', "some/topic", message="blah")
File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/subsystems/pubsub.py",
line 602, in publish
self._save_parameters(result.ident, **kwargs)
File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/subsystems/pubsub.py",
line 706, in _save_parameters
event = self.core().schedule(end_time, self._cancel_event, result_id)
File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/core.py",
line 409, in schedule
self._schedule_callback(deadline, event) File "/home/jenny/workspace/volttron/volttron/platform/vip/agent/core.py",
line 417, in _schedule_callback
self._schedule_event.set()
AttributeError: 'NoneType' object has no attribute 'set'
The closest to a solution I found is here RPC crashes with AttributeError: 'NoneType' object has no attribute 'call'. However, I notice they aren't exactly the same issue and so there isn't much surprise when I tried the solution offered there and it didn't work for me.
My code looks like this:
def sniffer(config_path, **kwargs):
''' Initializations '''
global pkt_counter
global IP_counter
# Defined other parameters here
class Sniffer(Agent):
def __init__(self, **kwargs):
super(Sniffer, self).__init__(**kwargs)
# I am just testing the publish function here
self.vip.pubsub.publish('pubsub', "some/topic", message="blah")
sniff(count=0, iface=conf.iface, prn = self.pkt_action, store=0)
def pkt_action(self, pkt):
#Process every packet, updates values and rises and alert if necessary
# some checks are run here and later a publish is called
Can someone please let me know what I'm doing wrong?
Edit: I didn't add that I want to run this script as I would a simple python script on the terminal (eg. python somescript.py): no installation. The reason I'm trying to do this is that I get an error when I install the agent and start it. The platform doesn't allow Scapy to create and connect to sockets.

Answer 1

You are attempting to use the vip module from in a context that isn't expected. The agent's lifecycle doesn't actually start executing until the start agent or configure events are triggered. Try to put the publish within those contexts.
The following excerpt is from the VOLTTRON readthedocs site located: https://volttron.readthedocs.io/en/develop/devguides/agent_development/Agent-Development-Cheatsheet.html#agent-lifecycle-events
Core Agent Functionality
These tools volttron.platform.vip.agent module. Try importing
Agent Lifecycle Events
Each agent has four events that are triggered at different stages of its life. These > are onsetup, onstart, onstop, and onfinish. Registering callbacks to these events are commonplace in agent development, with onstart being the most frequently used.
The easiest way to register a callback is with a function decorator:
#Core.receiver('onstart')
def function(self, sender, **kwargs):
function_body