Can't get SSDP discovery to work with a custom component

Development
1

Working on a custom integration for the BambuLabs printers. I can see in wireshark that its reguarly broadcasting notifications in response to the constant SSDP discovery message on my home network:

NOTIFY * HTTP/1.1
HOST: 239.255.255.250:1900
Server: Buildroot/2018.02-rc3 UPnP/1.0 ssdpd/1.8
Location: 10.10.10.81
NT: urn:bambulab-com:device:3dprinter:1
USN: <SERIAL>
Cache-Control: max-age=1800
DevModel.bambu.com: C11
DevName.bambu.com: 3DP-01S-557
DevSignal.bambu.com: -63
DevConnect.bambu.com: cloud
DevBind.bambu.com: occupied

But when I add ssdp to my manifest and created a basic async_step_ssdp() config_flow method, the printer is never offered up by HA as discovered. I know discovery works in my HA setup as it found my Unifi controller automatically a while back.

What am I missing? Does SSDP just not work for custom components?

Manifest content:
  "dependencies": ["mqtt", "ssdp"],
  "ssdp": [
    {
      "st": "urn:bambulab-com:device:3dprinter:1"
    }
  ]

Config flow for testing:

    async def async_step_ssdp(
        self, discovery_info: ssdp.SsdpServiceInfo
    ) -> FlowResult:
        """Handle ssdp discovery flow."""

        LOGGER.debug("async_step_ssdp");
        return await self.async_step_user()
2

I think you should be using NT not ST in the manifest file.

Manifest content:
  "dependencies": ["mqtt", "ssdp"],
  "ssdp": [
    {
      "nt": "urn:bambulab-com:device:3dprinter:1"
    }
  ]
3

From my research, ST is for the SSDP search request. NT is what gets returned in the notification responses. Regardless I did already try that and it didn’t work.

4

So I’m still confused by the SSDP implementation in home assistant. It looks like it only response to ST: responses initiated from a request it sends out? And ignores NT: notifications that are unsolicited?

But that’s probably moot. The SSDP notification from the Bambu printers gets set to ports 1990 and 2021 not the expected 1900. So even if home depot is listening for NT: it’s not going to see the payloads.