PDP-11 "Sockets: read error 9 - Bad file descriptor" on telnet logout with VH line set to HANGUP

[Terri-Kennedy]

On a Raspberry Pi 5 with 64-bit Bookworm running (locally compiled) Open-SIMH 6e9324e PDP-11, I have the simulator .ini script set up with:

;
; Set up the emulated DHU11 multiplexor    
set vh lines=16
set vh dhu
set vh modem
set vh hangup
set vh enable
attach vh 4000

On the PDP-11 OS side, I am running RSTS/E V10.1 with the relevant terminal lines set like this:

set terminal kbh0:/permanent/noautobaud/dialup/speed=19200

The Telnet client in both cases was a FreeBSD system named gate.

On logout from RSTS/E, the following is displayed:

Telnet session output:

$ bye
Saved all disk files on SY: 3808 blocks in use
Job 7 User 20,254 logged off KB17: at 14-Feb-26 06:13 PM
System RSTS V10.1-L SPC11D - 11/70
Run time was 0 seconds
Elapsed time was 1 minute
Good evening

Line hangup

Disconnected from the PDPConnection closed by foreign host.
gate:~terri# 

Console output:

>>>>>>>>>>>>>>>  OMS V10.1-A  14-Feb-26 06:13 PM  <<<<<<<<<<<<<<<
Message 12 from LOGOUT, user [0,0] on _KB17:, job 7
    LOGOUT terminating [20,254] on dial-up line KB17:
Sockets: read error 9 - Bad file descriptor

There are two issues here.

The first is the cosmetic missing CR/LF between "Disconnected from the PDP" and "Connection closed by foreign host". "Disconnected from the PDP" is likely also redundant as Open-SIMH is already reporting "Line hangup".

The second is the "Sockets: read error 9 - Bad file descriptor" which is being sent to the window where Open-SIMH was launched and is also the RSTS/E system console. This is definitely coming from Open-SIMH as RSTS/E has no 'file descriptor' naming convention for its files. Aside from being cosmetic, I'm concerned that this will cause Open-SIMH to either leak FDs or memory over time.

SIMH (presumably GitHub SIMH) V4.0-0 Current + REALCONS as supplied with the PiDP-11 distribution does not emit the "Disconnected from the PDP", only "Line hangup" and also does not emit the "bad file descriptor" error. So this appears to be a post-SIMH-split issue:

Telnet session output:

$ bye
Saved all disk files on SY: 3728 blocks in use
Job 8 User 20,254 logged off KB17: at 14-Feb-26 06:06 PM
1 other user still logged in under this account
System RSTS V10.1-L RSTS/E V10.1
Run time was 1 second
Elapsed time was 0 minutes
Good evening

Line hangup
Connection closed by foreign host.
gate:~terri# 

Console output:

>>>>>>>>>>>>>>>  OMS V10.1-A  14-Feb-26 06:06 PM  <<<<<<<<<<<<<<<
Message 8 from LOGOUT, user [0,0] on _KB17:, job 8
        LOGOUT terminating [20,254] on dial-up line KB17:

Remote access to both emulators is available if you need it to debug the issue. Alternatively, I can provide the .ini file and the RSTS/E disk image.