Thanks for that explanation. It's different from what the wired Duet does - but the wired Duet doesn't use the lwip socket interface. I presume I could replace the socket close call by a shutdown call to avoid the reset.
Some of the pictures are still direct links in the wiki, which need to be moved to proper wiki file references. Even then though images are fixed width, I will look to see if I can make media wiki display images responsively.