tn3270 permits a full-screen, full-duplex connection from a UNIX machine
to an IBM (or compatible) machine.  tn3270 gives the appearance of being
logged in to the remote machine from an IBM 3270 terminal.  Of course,
you must have an account on the machine to which you connect in order to
log in.  tn3270 looks to the user in many respects like the Yale ASCII
Terminal Communication System II.  tn3270 is actually a modification of
the ARPANET TELNET user interface (see telnet(1)) which will, in certain
circumstances, interpret and generate raw 3270 control streams.