Xnetlib makes use of the imake facility (via xmkmf) that comes with standard X Windows distributions. A generic Makefile is provided and can be used if imake is not present on your system.
After the executable is built, install it by copying the file xnetlib to an appropriate directory. There is no application defaults file to install.
With imake (xmkmf)
Type:
xmkmf
make
Without imake (xmkmf)
first edit Makefile.std to reflect your installation.
Then type:
make -f Makefile.std