On Mon, Dec 12, 2016 at 11:10 PM, Warner Losh <i...@bsdimp.com> wrote: > On Mon, Dec 12, 2016 at 11:04 AM, Seth Morabito > <lists+cct...@loomcom.com> wrote: >> Hi folks, >> >> I don't know if this is the best place to ask this question, but I don't >> know of any better forums for PDP-10 discussion, so hopefully it's >> on-topic enough. >> >> I recently set up the KLH10 PDP-10 emulator on my network, running >> TOPS-20 7.1. It's on a box in my 192.168.1.0/24 network. TCP/IP works >> great, I can telnet to it from within my network without any issue. >> >> I also set up my firewall (a box running CentOS 7.1) to port forward >> from external TCP port 2320 to internal TCP port 23 on the KLH10 box. >> >> Interestingly, when I telnet from _outside_ the network to my firewall's >> port 2320, it works, but Telnet goes into line mode rather than >> character mode! I can fix it with telnet escape (^]) by setting >> character mode explicitly with "mode character", but that's kind of >> annoying to do each time I connect. >> >> It feels like Telnet is no longer doing line mode / character mode >> negotiation when I'm port forwarding. It's most mysterious. >> >> If you want to see for yourself, you can telnet to >> gatekeeper.retronet.net 2320, which is the KLH10 instance. >> >> Does this ring any bells for anyone? > > I'm guessing that this is the classic "Many telnet clients default to > line mode for only for port 23." issue.
For a recent telnet in FreeBSD, I had to do a 'mode linemode' before it would behave like you are describing. Connect, hit return, hit the escape character (traditional one is ^]). mode linemode <return>. then I saw local echo and things looked approximately like I'd expect. Warner