[mosh-users] Mosh not reconnecting after standby

[Keith Winstein]

On Mon, Jun 17, 2013 at 3:28 PM, Florian Bruhin <me at the-compiler.org> wrote:
> * Keith Winstein <keithw at mit.edu> [2013-06-17 15:23:40 -0400]:
>> What version of mosh-client and mosh-server are you running, and on
>> what operating systems?
>
> Whoops, sorry for not mentioning that. It's definitely too hot to
> think here :P
>
> Both client and server are on the current git master (okay, actually
> they were two commits behind, but they shouldn't affect the issue -- I
> just upgraded and hope I'll run into it again soonish). --version says
> 1.2.4a.
>
> Both are running on an Arch Linux.

Ok, I think the first question when it happens again would be to
tcpdump at the client and server and figure out where packets aren't
getting through.

Question: Is there a NAT in between you and the server? Is it one you control?

Q: Is the server running any firewall rules? What are they?

At the client, you should see outgoing UDP packets to the server at
least every 3 seconds. They will be destined to a constant server port
(e.g. 60001), but the client-side source port may hop around about
every 20 seconds to different port numbers. Q: Do you see these
packets?

If things were working, at the client you would also see packets from
the server, with a source port that's constant (e.g. 60001) and a
destination that matches a recent source port from the client. Q: Do
you see these packets?

Now tcpdumping at the server, you should see incoming UDP packets from
the client. Q: Do you see these packets?

If so, you should also see outgoing packets from the server back to
the client. Q: Do you see these packets?

The final question is Q: What does the line in "who" from the server
look like? Does it reflect an attached client or not?

Hopefully we can isolate what the problem is this way!

Cheers, and thanks for chasing this down,
Keith