[TUHS] BSD 2.11 on PDP11/70 (emulated), connecting to it via a slip interface

[Rik Farrow via TUHS]

IIRC, telnet might be started by inetd, configured in /etc/inetd.con. It
handles connections (and the built-in, like echo) and then passes the
connection off to the actual telnetd. I suggest taking a look there, and
making sure you have the actual server...

Rik


On Mon, Apr 13, 2026 at 2:13 AM Folkert van Heusden via TUHS <tuhs at tuhs.org>
wrote:

> Hi,
>
> As I mentioned a year ago I'm working on a pdp11/70 emulator. Just for
> fun, not serious like simh.
>
> Currently it can run BSD 2.11 multiuser on an ESP32-S3 (altough booting
> takes almost 50 minutes on that platform).
>
> It also runs on Linux etc. So I setup a BSD kernel with slip and dz11
> support to allow telnet over IP with slip. Unfortunately that hangs. I
> can ping, I can nmap the virtual PDP but telnet to the PDP just does
> SYN/SYNACK/ACK and then nothing. Any ideas why telnet would hang?
>
> Pinging the pdp:
>
> root at snsv:~# ping 192.168.1.2
> PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
> 64 bytes from 192.168.1.2: icmp_seq=1 ttl=255 time=77.5 ms
> 64 bytes from 192.168.1.2: icmp_seq=2 ttl=255 time=185 ms
> 64 bytes from 192.168.1.2: icmp_seq=3 ttl=255 time=90.2 ms
> ^C
> --- 192.168.1.2 ping statistics ---
> 3 packets transmitted, 3 received, 0% packet loss, time 2004ms
> rtt min/avg/max/mdev = 77.503/117.547/184.895/47.905 ms
>
> nmap:
>
> Nmap scan report for 192.168.1.2
> Host is up (0.069s latency).
> Not shown: 990 closed tcp ports (reset)
> PORT    STATE SERVICE
> 1/tcp   open  tcpmux
> 7/tcp   open  echo
> 9/tcp   open  discard
> 21/tcp  open  ftp
> 23/tcp  open  telnet
> 79/tcp  open  finger
> 113/tcp open  ident
> 513/tcp open  login
> 514/tcp open  shell
> 515/tcp open  printer
> Device type: general purpose
> Running (JUST GUESSING): BSD 2.X (85%)
> OS CPE: cpe:/o:bsd:bsd:2.11
> Aggressive OS guesses: 2.11BSD (85%)
> No exact OS matches for host (test conditions non-ideal).
>
> OS detection performed. Please report any incorrect results at
> https://nmap.org/submit/ .
> Nmap done: 1 IP address (1 host up) scanned in 27.90 seconds
>
> telnet network trace:
>
> 10:39:41.390230 IP 192.168.1.1.55606 > 192.168.1.2.23: Flags [S], seq
> 730571314, win 65535, options [mss 256,sackOK,TS val 1346414773 ecr
> 0,nop,wscale 10], length 0
> 10:39:41.458696 IP 192.168.1.2.23 > 192.168.1.1.55606: Flags [S.], seq
> 43457, ack 730571315, win 4096, options [mss 966], length 0
> 10:39:41.458753 IP 192.168.1.1.55606 > 192.168.1.2.23: Flags [.], ack 1,
> win 65535, length 0
> 10:39:41.459364 IP 192.168.1.1.55606 > 192.168.1.2.23: Flags [P.], seq
> 1:31, ack 1, win 65535, length 30 [telnet DO ENCRYPT, WILL ENCRYPT, DO
> SUPPRESS GO AHEAD, WILL TERMINAL TYPE, WILL NAWS, WILL TSPEED, WILL
> LFLOW, WILL LINEMODE, WILL NEW-ENVIRON, DO STATUS]
> 10:39:42.035173 IP 192.168.1.1.55606 > 192.168.1.2.23: Flags [P.], seq
> 1:31, ack 1, win 65535, length 30 [telnet DO ENCRYPT, WILL ENCRYPT, DO
> SUPPRESS GO AHEAD, WILL TERMINAL TYPE, WILL NAWS, WILL TSPEED, WILL
> LFLOW, WILL LINEMODE, WILL NEW-ENVIRON, DO STATUS]
> 10:39:43.123157 IP 192.168.1.1.55606 > 192.168.1.2.23: Flags [P.], seq
> 1:31, ack 1, win 65535, length 30 [telnet DO ENCRYPT, WILL ENCRYPT, DO
> SUPPRESS GO AHEAD, WILL TERMINAL TYPE, WILL NAWS, WILL TSPEED, WILL
> LFLOW, WILL LINEMODE, WILL NEW-ENVIRON, DO STATUS]
> ...
>
> regards
>
> --
> www.vanheusden.com [1]
>
> Links:
> ------
> [1] http://www.vanheusden.com
>