Você precisa usar Telnet . Para sua sorte, existe uma ferramenta para isso chamada x3270 - ferramenta de acesso de host IBM .
x3270 opens a telnet connection to an IBM host in an X window. It
implements RFCs 2355 (TN3270E), 1576 (TN3270) and 1646 (LU name
selection), and supports IND$FILE file transfer. The window created by
x3270 can use its own font for displaying characters, so it is a fairly
accurate representation of an IBM 3278 or 3279. It is similar to
tn3270(1) except that it is X-based, not curses-based.
The full syntax for host is:
[prefix:]...[LUname@]hostname[:port]
Instalação ( x3270 )
sudo apt-get install x3270
De acordo com as informações do Ubuntu Software Center, você precisará instalar as fontes x3270 manualmente, uma vez que elas são necessárias ( xfonts-x3270-misc ):
sudo apt-get install xfonts-x3270-misc