How to locally resume a session that has been started remotely using xrdp?

xrdp runs xvnc over rdp and does so very well. The default configuration launches a new xvnc session on each connection, starting at port 5910. To get it to reconnect to an existing session, edit /etc/xrdp/xrdp.ini thusly:

[xrdp1]
name=sesman-Xvnc
lib=libvnc.so
username=ask
password=ask
ip=127.0.0.1
port=ask5910

This way it asks for the port with a default of 5910. If no vnc session exists on 5910 then a 5910 connection attempt will fail. In that case try again, but set the port to -1 to force the creation of a new session, typically on 5910.