They control to what address vsmserver/vsmagent binds to, which can be useful to limit ThinLinc traffic to certain networks.
We also should consider removing them. In many cases it will be insufficient to bind to a single address, so full functionality would mean changing the architecture to support multiple listening sockets. Better to use a local firewall in that case.
Decided to implement this as a trivial bug. I decided to remove the parameters instead of adding documentation, based on the reasoning in comment #1.
"git grep listen_hostname" finds nothing in the ctc tree any longer, so I'm calling this done.
Confirmed that there are no traces of "listen_hostname" left. Also checked that the services bind properly, with and without IPv6 enabled on the system.