Thus said Max Clark on Sat, 13 Nov 2010 07:54:00 PST:

quoted text
> I've  experimented  with  tcpserver  from the  ucspi  package  without
> success. How  do I  give access  to the  bgplgsh application  only via
> telnet?

Probably because  you are missing a  tty. If you also  install ptyget[1]
you might be able to accomplish it with something like:

tcpserver -v 0 1234 ptyrun /usr/bin/login -f -u bgplg bgplg

or maybe:

tcpserver -u `id -u bgplg` -g `id -g bgplg` -v 0 1234 ptyrun /usr/bin/bgplgsh

Andy

[1] http://cr.yp.to/software/ptyget-0.50.tar.gz