telnet v.s. rlogin


jam@radc-lonex.arpa
Tue, 25 Oct 88 16:13:43 EDT


>henry@zoo.toronto.edu writes:
>
>One unfortunate problem is that Berkeley rlogin is definitely a better
>implementation than Berkeley telnet. If you compare sources, it's fairly
>obvious that rlogind is probably derived from telnetd, but various fixes
>and improvements in rlogind have not found their way back into telnetd.
>At least, not in the Sun sources that we have (VAXen are a vanishing
>breed around here and I don't have any convenient way to check out the
>current Berkeley sources).

The current Berkeley sources aren't that much different, though a fuller
implementation of the telnet features had been added with 4.3.

HOWEVER, the rlogin and telnet protocols differ in one major aspect (along
with a few minor ones...). The design of telnet implies that data is
always sent in segments with a line terminator. This is good with hardware
like IBM, but not good at all if you want to run software that peeks at
exactly what the keyboard is sending. Rlogin is much simpler in nature,
and just passes whatever is typed at the keyboard. You press <CR>, the
host software gets <CR>. Telnet would translate that to an end-of-line
sequence, which is open to interpertation on the other end.

Almost a year ago there was discussion of adding a mode to telnet that
would handle a terminal like rlogin. Sort of a RAW data mode without
the stipulations that telnet places on that mode. This never came about.
Perhaps more people just took to using rlogin?

Joel A. Mussman
jam@radc-lonex.arpa



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