I fired up a MKRWAN1300 today and started experimenting with the example code. One thing I have noticed is that the port number changes from time to time. I've seen uplinks using port number 2, 4 and 6. Looking further into this, I cannot find the API for setting the port number.
If you're going to do that then please be considerate enough to add links to the other places you cross posted. This will let us avoid wasting time due to duplicate effort and also help others who have the same questions and find your post to discover all the relevant information. When you post links please always use the chain links icon on the toolbar to make them clickable.