Why is UPnPy discover throwing AttributeError?

Question

I am working with UPnPy, and I immediately notice an issue when attempting to discover devices on my local network. Here is the basic code I am using:

import upnpy

upnp = upnpy.UPnP()

devices = upnp.discover()

This throws the following exception:

Traceback (most recent call last):
  File "C:\Users\name\Projects\pythonProject\main.py", line 5, in <module>
    devices = upnp.discover()
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\upnp\UPnP.py", line 33, in discover
    for device in self.ssdp.m_search(discover_delay=delay, st='upnp:rootdevice', **headers):
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\ssdp\SSDPRequest.py", line 50, in m_search
    devices = self._send_request(self._get_raw_request())
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\ssdp\SSDPRequest.py", line 100, in _send_request
    device = SSDPDevice(addr, response.decode())
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\ssdp\SSDPDevice.py", line 87, in __init__
    self._get_services_request()
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\ssdp\SSDPDevice.py", line 23, in wrapper
    return func(device, *args, **kwargs)
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\ssdp\SSDPDevice.py", line 54, in wrapper
    return func(instance, *args, **kwargs)
  File "C:\Users\name\Projects\pythonProject\venv\lib\site-packages\upnpy\ssdp\SSDPDevice.py", line 171, in _get_services_request
    event_sub_url = service.getElementsByTagName('eventSubURL')[0].firstChild.nodeValue
AttributeError: 'NoneType' object has no attribute 'nodeValue'

I have been researching the cause of this but I have found nothing. I am using UPnPy version 1.1.8. I use PyCharm as my IDE. I've tried using previous versions of UPnPy but none seem to be working. Any help would be appreciated. Thanks!

Answer 1

Most likely you have a non-compliant UPnP Device in your home network that is serving a non-standard/broken XML at their description location, and upnpy was not smart enough to handle the parsing error and perhaps ignore that device.

That scenario is more common than you might think: many Smart TVs (LG ones for sure) have an embedded device that advertises as UPnP but their description endpoint answers JSON instead of XML!

Some suggestions:

• Use a different library or app (you could try my own), at least to identify the culprit. Check turn on verbosity and look for warnings and parsing error logs
• Use a scanner such as tcpdump to sniff network packets (UDP port 1900) for SSDP NOTICE advertises, and manually open each LOCATION URL in a browser to see if they're valid XML
• Selectively turn off / unplug devices you think might be UPnP-enabled, such as Smart TVs, Home Theaters, Video Game consoles, Routers, etc, to see wich one was serving the bogus XML.
• Edit your local copy of upnpy to handle that error, for example enclose the function/line with a try/except block and print some details about what is it trying to parse prior to the error.