What are port requirements for remote lisp?

[Martin Simmons]

>>>>> On Wed, 1 Apr 2020 08:59:30 -0400, Mirko Vukovic said:
> 
> On Tue, Mar 31, 2020 at 11:51 AM Martin Simmons <martin at lispworks.com>
> wrote:
> 
> > >>>>> On Mon, 30 Mar 2020 21:16:00 -0400, Mirko Vukovic said:
> > >
> > > Hello,
> > >
> > > My setup is Sly on Spacemacs with Windows 10 running remote lisp on Linux
> > > over a corporate network. I have not found a Sly mailing list, and I
> > hope I
> > > can get an answer here.
> > >
> > > Emacs is running Sly on Spacemacs on Windows 10. Lisp is running on a
> > Linux
> > > server. But Sly does not connect to the listening Lisp. Corporate network
> > > security policies have changed. I can ask for IT to accommodate me, but
> > > first I need to know what to ask for.
> > >
> > > So far, I have opened a tunnel, and started a listening lisp (details
> > > below).
> > >
> > > In Emacs I get:
> > >
> > > sly-connect RET RET RET
> > > [sly] Connecting to Slynk on port 4005..
> > > helm-M-x-execute-command: make client process failed: Connection timed
> > out,
> > > :name, sly-9, :buffer, nil, :host, hal9000, :service, 4005, :nowait, nil,
> > > :tls-parameters, nil
> > >
> > > The session transcript:
> > > > ssh -L4005:localhost:4005 mirko at hal9000
> > >
> > > [mirko at hal9000 .roswell]$ ros -L ccl-bin run --load
> > start-slynk-server.lisp
> > >
> > >  Added SLYNK path to ASDF:*CENTRAL-REGISTRY*
> > > SLYNK's ASDF loader finished.
> > >  Loaded ASDF system
> > > ;; Slynk started at port: 4005.
> > >
> > >  Created SLYNK server on port 4005
> > >  Set *USE-DEDICATED-OUTPUT-STREAM* to NIL
> > > Clozure Common Lisp Version 1.11.5/v1.11.5  (LinuxX8664)
> > >
> > > For more information about CCL, please see http://ccl.clozure.com.
> > >
> > > CCL is free software.  It is distributed under the terms of the Apache
> > > Licence, Version 2.0.
> > > ?
> > >
> > > My question is as follows:
> > >
> > >    1. Do I need bi-directional traffic on 4005?
> >
> > Assuming you are using the ssh tunnel above, then you don't need port 4005
> > traffic on the LAN (it is all hidden in the tunnel).
> >
> > The most likely problem is that some firewall on the Windows machine is
> > blocking port 4005.  You may need to configure that firewall to allow ssh
> > to
> > listen on localhost:4005 and/or to accept connections to it from Spacemacs.
> > In theory you might have similar localhost firewall issues on hal9000, but
> > that is less likely.
> >
> >
> > >    2. Do I need bi-directional traffic on 22? (after recent changes I
> > >    cannot ssh or scp into my Windows machine)
> >
> > I'm assuming that you ran the ssh command on the Windows 10 machine and it
> > gave you a working login to hal9000.  If so, then it looks like you already
> > have what you need for port 22.
> >
> 
> Yes, I can log in to hal9000 with the -L switch:
> 
> > ssh -L4005:localhost:4005 mirko at hal9000
> Last login: Thu Mar 19 14:33:17 2020 from 172.27.236.189
> [mirko at hal9000 ~]$
> 
> 
> >
> > Note that bi-directional traffic on a connected socket is different from
> > whether you can make a connection in both directions.
> >
> >
> > >    3. What tools can I use to try to narrow down the cause of the
> > problem?
> > >    For instance, can I send a command to the lisp image, and see its
> > effects
> > >    on the lisp side?
> >
> > Firstly, run "netstat -antp" on hal9000 to see if Lisp is listening on port
> > 4005.
> >
> 
> It looks that ccl-bin is listening:
> $ sudo netstat -antp | grep :4005
> tcp        0      0 127.0.0.1:4005          0.0.0.0:*               LISTEN
>      104461/lx86cl64
> 
> 
> >
> > Secondly, run "netstat -anop tcp" on the Windows 10 machine to see if ssh
> > is
> > listening on port 4005.
> >
> >
> I have Msys2's netstat. On the laptop:
> > which netstat
> /c/WINDOWS/system32/netstat
> /c/Users/mirko/Downloads
> > netstat -anop tcp | grep :4005
>   TCP    127.0.0.1:4005         0.0.0.0:0              LISTENING       12052

Yes, both netstat outputs look good at that point.


> > Thirdly, run "ssh -p 4005 localhost" on the Windows 10 machine.  This use a
> > ssh is very bogus, but it should at least give an error message with some
> > diagnostics.  (Normally I would use telnet for this, but it is not
> > installed
> > on Windows 10 by default.)
> >
> 
> Outputs of both ssh and telnet on the laptop:
> > which telnet
> /usr/bin/telnet
> /c/Users/mirko/Downloads
> > telnet localhost 4005
> Trying ::1...
> Connected to localhost.
> Escape character is '^]'.
> Connection closed by foreign host.

OK, so it is connected to the Windows side at least.

Check that the Slynk server was created with :dont-close t (or set
slynk:*dont-close* to t before creating it).  If dont-close is nil, it will
only accept one connection, which makes debugging difficult.

Then restart the log in to hal9000 with -v option to ssh to make it print debug
information:

ssh -v -L4005:localhost:4005 mirko at hal9000

and try the telnet again to see what is happening at the Linux end.

__Martin