Is it possible to send UDP or TCP packet, by using Payload decoder function?
For example decoded GPS coordinates into GSP tracking server?
No, this is (and should) not possible. Its only purpose is to decode from a slice of bytes into a JSON object. In case you want to make a request to your GPS tracking server I would suggest to do this at your application side (after receiving the data either using MQTT or an HTTP integration).
OK. I am understand.
I need to develop standalone gateway, between mqtt and Tracking server.
Node-red solves the problem.