ssh – Dr John's Tech Talk

Web to ssh gateway – not so difficult with Right Tools

Intro
I won’t go into details in this posting for fear that the “bad people” will be more likely to benefit than the legitimate users of what I’m describing. That being said there are some legitimate uses, for instance when you need that terminal access but a direct ssh connection just isn’t available.

Ajaxterm
I’m kind of amazed at how far Javascript has come. You can implement a curses-based application in javascript, i.e., a terminal console? Yup. You bet. And the kicker is that it works quite well. Teraterm it ain’t, but I’ll be danged if you can’t vi a file, run top as well your basic commands, all over a pretty standard-looking web page. That’s what we mean by gateway – an application which converts one protocol to another. In this case HTTP to shell (I suppose).

The generic application is called ajaxterm. I used it from a distribution that runs a local python server on my server. It’s described here:

https://github.com/antonylesuisse/qweb/tree/master/ajaxterm/README.txt

If you keep the default screen size, 80×24, he says it has few enough characters that a screen refresh can be contained in one packet. In my testing the echo delay was probably under one quarter second.

Forget about a scroll bar holding 1000’s of lines, however. You get just your basic terminal like in the old days.

Someone reminded me about screen, which I hadn’t been using. Screen is an extremely useful tool. It’s like a terminal multiplexor. Now I normally set up my screen escape sequence to be Ctrl-\, but for some reason this particular sequence is not recognized by Ajaxterm. What I settled on instead is Ctrl-g (escape ^Gg in your .screenrc). I don’t like to use the default Ctrl-a because this is a useful emacs editing mode sequence – takes you to beginning of line. Popping between screens is a little slow with ajaxterm as might be expected. It’s a worst-case, everything must be re-drawn situation, I suppose. But ajaxterm + screen is a pretty powerful combination.

Conclusion
Now I have an additional path to my server’s command line if a direct ssh connection isn’t available.

An SSH Terminal App for the HP Touchpad

October, 2016 Update
Needless to say, the HP Touchpad never caught on and mine is collecting dust.

What I just got is the new 8″ Amazon Fire HD Tablet. You can get a free good-quality ssh client for it called serverauditor. The keyboard emulation (linux CLI needs all those unusual keys pretty badly). The battery life is genuinely good – better than the Touchpad. It’s $89.

I’ll keep the blog post below online for historical purposes.

Updated Version
My previous post got out-of-date so rapidly that I have to start this topic all over! DO NOT follow my previous advice.

The Bluetooth Keyboard – It’s Worth It
My Bluetooth keyboard came in. It’s really awesome. I advise to get it if you want to treat your Touchpad (the cognoscenti prefer TP) like a Netbook from time-to-time, namely, by having the ability to type rapidly and comfortably. Get the HP one made for the Touchpad because:
– it’s small like you’d expect as a companion for a small tablet computer, yet the keys are full size
– it has some really convenient shortcut keys so you’re not spending too much time shifting your hand from keyboard to screen, namely:
— volume controls
— screen on/off
— even a key that shows your cards
– plus some keys that do stuff that’s harder with just a TP
— Ctrl (control) key, yeah!
— arrow keys
–mute key
–screen brightness/dimmer keys
–plus other keys I haven’t tested yet
– and the : and / keys are primary keys like they should be

So far I’m missing a
-Home/End key and if I ever get my terminal working again
– an ESC (escape) key

All-in-all I’d say the Bluetooth keyboard is an obviously well-engineered product – a perfect pairing for the TP.

It’s $45 at Amazon. And yes, I am writing this blog entry on my new keyboard!

I also bought an off-brand display stand. By Mivizu. It’s better than NOT having one, but it’s kind of flimsy and awkward. In no way a fun and beautifully engineered companion to the TP, unlike the IPad case that everyone likes to play with.

What About that SSH Terminal?
I probably messed things up with Preware alpha/beta software. They have released an Xterm, but I arrived at it from various previous upgrades and either Xecutah or the XServer is not working for me. The XServer does not launch a new card like it should. See below.

I will probably have to Web Dr my device (start from a factory install state), which they warn you should be prepared to do when using test software. Live and learn. I have not had time to do that yet, but I wanted to delete my old post and get the new facts out here before others went down the wrong path.

So, briefly, an ssh, bash, xterm to your underlying Linux on your TP are all available from the webos-internals.org site.

Sep 29th I saw an upgrade for Xecutah, Servers and xterm – to v 0.9.3. I did the upgrade and, to my surprise, I am back in business again! The xterm launches once again and so I do not have to Web Dr my Touchpad.

I thought I owed it to the community to experiment, so I decided to change root’s shell to bash! That’s right, the shell is that old /bin/sh by default. Once you’ve installed it, bash appears in /opt/bin/bash. Well…that worked too. I now have a comfortable shell that launches for me when I fire up my xterm, or xterms. Of course I brought over my .bashrc file – using sftp of course – with its familiar prompt definition and convenience aliases such as the universal “ll” for ls -l. To make really sure I hadn’t blown up my Touchpad, I rebooted. Yes, reboot from your shell really does work to reboot your TP! And yes, it came back with flying colors.

Esc key in the xterm for real Keyboard Users
I don’t think the HP keyboard has an escape key, not that I can find. So you’re in a bit of a bind if you use it for your xterm during a vi editing session. What you can do is momentarily bring up the virtual keyboard by hitting the, um, keyboard key. Xecutah now comes with instructions on how to generate the escape key on the virtual keyboard (hold t, choose right-most character, then “[” as your next character) which work. Then, when you’ve got your Esc, which you don’t need to often anyways, hit that keyboard key again to recommended using your comfy real keyboard.

So I am a happier camper once again. I even contributed to webos-internals. You should, too, if you think they’re providing a valued service as I do.

To be continued.