Getting mqtt data from wifi

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Are you capturing on the device transmitting and receiving the MQTT data or are you capturing on another device and attempting to sniff the WiFi transmissions?

Ultimate goal is to decode LG HVAC communication. Right now I'm using a Raspberry Pi3 with Kali Linux and modified kernel for monitor mode. Home network is Mosquitto talking to other Pis and Wemos temperature sensors and Sonoff switches running Tasmota firmware. Used Wireshark about 5 years ago, but never for 802.11.

To confirm, "for monitor mode" means you're sniffing transmissions on other devices.

If that's the case then you should look at the Wiki page on WLAN capturing.

Sharing a capture on a public fileshare, e.g. Google Drive, DropBox etc.), and posting a link to it back here will help others to analyse your issue.

Had to make another network for sending a trace....

Devices:

192.168.1.1 - Enigma Netgear N150 Router (not connected to internet) 
192.168.1.2 - Lenovo Android (sending On/Off commands via Node-Red dashboard)
192.168.1.3 - Sonoff (tasmota firmware, turns light On/Off)
192.168.1.4 - HP Not doing anything - just on network
192.168.1.6 - Wemos DS18b20 temp sensor TelePeriod set for 15 seconds
192.168.1.7 - Pi3+ running Node-Red and Mosquitto

Trace was captured while I cycled power to the Sonoff 5 times. Temperature from Wemos then was raised from 68.3 to 69.2 F, (TelePeriod sends data every 15 seconds), then the trace was terminated.

Terminal command:

tcpdump -1 wlan0mon -w tcdump

Trace run from Raspberry Pi3+ Kali Linux with patched kernel for monitor mode on internal wifi controller.

https://www.dropbox.com/s/bp7s3z9u155...