Re: Using tramp to connect to a remote emacs session

[Suvayu Ali <fatkasuvayu+linux@gmail.com>]

Hi Michael,

On Friday 04 September 2009 12:03 AM, Michael Albinus wrote:
> Suvayu Ali<fatkasuvayu+linux@gmail.com>  writes:
>
>> Correct me if I go wrong, when I issue that command emacsclient tells
>> the remote server to connect with the localhost over tramp. It
>> determines where the remote server is from the server file.
>
> Yes.
>
>> My problem is my ISP at the local machine doesn't allow me to login to
>> it from outside. In other words I probably don't have a static ip. So
>> when I issue the command I get,
>>
>>> $ emacsclient /ssh:user@local.host:~/file
>>> emacsclient: connect: Connection refused
>>> emacsclient: connected to remote socket at xxx.xx.xxx.xx
>>> Waiting for Emacs...
>>>
>>> *ERROR*: Process died
>
> So at least emacsclient was able to connect your remote server. Good.
>
>> And on the remote machine I get the following in the *Messages* buffer,
>>
>>> Tramp: Opening connection for user@local.host using ssh...
>>> Tramp: Waiting 60s for local shell to come up...
>>> Tramp: Sending command `ssh local.host -l user  -q -e none&&  exit || exit'
>>> Tramp: Waiting for prompts from remote shell
>>> File error: Process died
>
> That I do not catch. Are the messages exactly as you have written, or
> did you exchange the real user and host name by "user" and "local.host"?
>
My lab is a bit paranoid about security so I edited out the specifics 
and put in generic names. :)

> Note, that "user" shall be the user name you run your local host, and
> "local.host" must be an FQDN of your host, or an IP address.
>
The host name for my localhost is limited to the local network. The 
Siemens router from my ISP (Telus) probably implements some kind of NAT 
(I'm not sure). So the outgoing connection worked, whereas the incoming 
connection failed.

>> So to summarize my problem is I can only connect one way, local.host to
>> remote machine, and hence tramp fails to work. Does this mean the only
>> way I will get this working is to get my ISP to give me a static ip?
>
> You have mentioned two different explanations. Either your ISP does not
> allow you to login from the outside. Then we could stop. But usually,
> they don't forbid it.
>

I don't have a static IP, moreover from the outside I can only see my 
ISP's servers not my home machine. Hence I can't login from the outside.

> If you have a dynamic IP address (the other possiblitiy), you could run
>
>    emacsclient /ssh:user@1.2.3.4:/file/to/edit
>
> "1.2.3.4" would be the IP address you are currently using. Because this
> changes day by day, you might evaluate it every time in a script,
> starting emacsclient.
>
> The more simple solution is to register your local machine with dynamic
> DNS. Let's say you have registered it at http://www.dyndns.com/, under
> the name "suvayu.homelinux.org" (just as example). Then you could
> connect via
>
>    emacsclient /ssh:user@suvayu.homelinux.org:/file/to/edit
>

This is very interesting. I had no idea such a service existed! I will 
definitely look into this.

> Another trap you could enter is your router configuration at home. You
> must allow incoming connections at port 22 (for ssh), and it must be
> forwarded to your local host.
>

I can login to my router's admin interface, so that should not be 
difficult to setup.

Thanks for your patience. :)

-- 
Suvayu

Open source is the future. It sets us free.