Xtrans includes a number of routines to make x implementations transport-independent; at time of writing, it includes support for unix sockets, ipv4, ipv6, and decnet.

xtrans is not actually a library in itself; it includes .c files which are then used in the compilation of x servers, libraries, et al.

more information about x.org can be found at:

this module can be found at git://anongit.freedesktop.org/git/xorg/lib/libxtrans