Sending 0377 via KL8JA

Christian Corti cc at
Tue Jan 20 03:54:42 CST 2015

On Mon, 19 Jan 2015, Kyle Owen wrote:
> Run 'nc localhost 2222 | od -to1' in a terminal, then 'go 200' and
> repeatedly press 'c', seeing how many times it takes to generate a line of
> characters in 'od'. Then, 'd sr 0376' and confirm that it takes twice as
> many presses, indicating half as many characters being sent per TLS
> instruction with the latter.

Of course this is normal behaviour. You need to use a client that
*correctly* implements the TELNET protocol. In your case, sending 377 as a
data byte needs duplication because a single 377 is the TELNET IAC escape
character. This is handled by the TELNET server implemented in SIMH.
Note: netcat (or nc) has never correctly implemented the TELNET protocol.
It fails when using binary mode. And curl has problems, too (in some cases
it loses NULL bytes etc.). The only client that doesn't have any problems
with TELNET is C-Kermit.


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