Sometime ago I found a patch in a mailinglist that replaces the TCP/IP socket communication with a UNIX Domain socket.
It was ultimatly rejected because, the original author did not recreate the patch after a major rework of the TCP/IP code.
For my my usecases I recreated that functionality on a recent version (0.3.14) of Trousers
After some feedback from colleagues, I revised my patch and removed the necesity to decide at compile time, if support for UNIX Socket is compiled, insted it is treated the same as INET and INET6 sockets, with an option in the configuration option, that allows it to be disabled