Can't find MDNS device from Android Phones and ESP32 Devices

[MikaAK]

Issue

I'm having an issue where my nerves device is not found by Android Phones or ESP32 devices. I've tested a total of 7 devices with the following results:

Devices That Worked

IPad, Mac Book Pro, Windows 10 Laptop, Windows 10 PC

Devices That Didn't Work

Galaxy S10 Android, Huawei P10 Android, ESP32 module

Info

@fhunleth Mentioned

It could be that mdns_lite’s advertisements are RFC legal, but perhaps slightly different from everyone else’s so the mDNS stack on a constrained device like the ESP32 doesn’t like them

Config

The only config for mdns_lite I've done is setting the host

Steps Taken

I used this android app Network Analyzer to try and sniff out a bit more info.

Doing a LAN Scan, I do see the device listed under the proper name however I'm unable to find it in Chrome it just shows an NXDOMAIN error.

I've tried adding a new service for HTTP as well but that didn't work.

config :nerves_pack, :services, [%{
  name: "Web Server",
  protocol: "http",
  transport: "tcp",
  port: 80,
}, %{
  name: "SSH Remote Login Protocol",
  protocol: "ssh",
  transport: "tcp",
  port: 22
}, %{
  name: "Secure File Transfer Protocol over SSH",
  protocol: "sftp-ssh",
  transport: "tcp",
  port: 22
}, %{
  name: "Erlang Port Mapper Daemon",
  protocol: "epmd",
  transport: "tcp",
  port: 4369
}]

I wasn't able to figure out MDNS logging with the ESP32, though I'm sure there has to be a way to turn it on, I'm just using Arduino to code it. If anyone has any ideas that would be great!!

[fhunleth]

Is it the service discovery part of mDNS that's not working or a mDNS name lookup that's not working? I.e., are you trying to resolve nerves.local or nerves-wxyz.local or are you trying to discover the ssh service on your network?

Unfortunately, I don't have any Android or ESP32 devices so I can't reproduce.

[MikaAK]

Well, this is an interesting issue. It turns out Android and mDNS in the browser are not friends https://bugs.chromium.org/p/chromium/issues/detail?id=405925.

For ESP32 it seems you can't use raw nerves.local URLs, you must resolve the IP first then do a lookup using the following docs:
https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/protocols/mdns.html#mdns-query

I'll leave both those here for anyone looking at this in the future 😄

[fhunleth]

Thanks for following up and that link to the chromium thread.