[Bug] Missing IGMP message to join group 224.0.1.187
**Describe the bug**
I have an issue with CoAP messages not being passed to my HOOBS Raspberry Pi4 by a TP-Link Deco P7 mesh router. TP-Link support has now very kindly helped me to troubleshoot this issue. They claim that the root cause is that the RPi never send an IGMP message to join group broadcast group 224.0.1.187. I am not sure if the join message should be sent by this plug-in or by HOOBS.

**Environment:**
 - Shelly device(s): 1, i3, 4Pro
 - Plugin version: 0.16
 - Device running homebridge: Raspberry Pi4 HOOBS 3.3.2