Pre-/Post-script support / termux integration

[PureIncompetence]

I wondered if a termux integration to be able to run pre-defined pre- and post scripts for VNC connections could be added to AVNC. Full-fledged desktop vnc clients like remmina offer to run pre/post scripts for saved connections, although this probably would be somewhat harder to implement on our own due to android platform limitations.

The probably most feature complete and used terminal application for android - Termux - offers an API for other apps to execute commands in its shell environment: https://github.com/termux/termux-app/wiki/RUN_COMMAND-Intent
That would probably be easier and more useful to implement.

Use-Cases that would profit from it:

1. Wake-On-LAN before connecting / shutdown via SSH after closing the connection. The first one is already implemented in AVNC as a GUI option.
2. An actual use-case I'd like to have it available for: I've got a terrible vnc server on an embedded device I cant fix. It segfaults whenever a client disconnects. Meaning: Whenever I want to connect to it via VNC I first have to connect via SSH and start the server (again). When connecting to the device via Remmina, that works fully transparent using a pre-script.
3. A hypothetical use-case which is also already integrated into AVNC: SSH-tunneled connections - before I found AVNC when I had to use a proprietary vnc client and wanted to connect to a vnc server through ssh I had to run a seperate termux script setting up a port forwarding first. That script had to run with root access to be able to monitor when I closed the vnc client so it could afterwards close the ssh connection and exit. Thanks to the SSH integration in AVNC, this is not necessary anymore, but it shows the quirky workarounds needed if "pre-scripts" need to be run independently. Edit: This would also allow for pre-scripts setting up ssh connections through jumphosts as were asked for in Feature request: Support for ssh jump hosts #191.

I'm not sure if that is too much of a niche use case to justify the effort of adding it to / maintaining it in AVNC, thats why I opened this discussion instead of creating a feature request.

Thank you very much for creating / maintaining this great piece of software. As mentioned above it already makes using vnc on android much more hassle-free / convenient that it ever was before by eliminating the need to build additional workarounds around it.

[gujjwal00]

Adding full fledged Termux support is a bigger task. Actual command invocations looks simple enough, but the UI around it will likely be more time consuming. To be completely honest, I probably won't work on this.

An alternative could be to execute a command via SSH directly on server. AVNC could execute the command just before starting the VNC session.

In your specific case, are you able to setup a "watchdog" process to restart VNC server after crash? Something like a systemd service or a cron job.

[PureIncompetence]

Adding full fledged Termux support is a bigger task. Actual command invocations looks simple enough, but the UI around it will likely be more time consuming. To be completely honest, I probably won't work on this.

I see. Maybe we could leave the discussion open in case anyone else with sufficient coding skills might want to take it up or in the future you're running out of ideas on features that would set AVNC even wider apart from every other vnc client out there. 😉

An alternative could be to execute a command via SSH directly on server. AVNC could execute the command just before starting the VNC session.

That could actually be helpful for some of the cases I mentioned.

In your specific case, are you able to setup a "watchdog" process to restart VNC server after crash? Something like a systemd service or a cron job.

I've tried doing so first, but didnt find a way that worked.
For now I've worked around it by creating a termux shortcut script which is starting the vnc server on the target host and afterwards calling a vnc:// uri so AVNC opens the saved connection of that host. That works like 9 out of 10 times. (probably need a bigger delay between the two commands)
Its not as clean as a pre-script would be (It requires a seperate shortcut on the homescreen for that target host and obviously doesnt work when chosing that host from inside of AVNC.), but it works for my use-case.

[gujjwal00]

Maybe we could leave the discussion open in case anyone else with sufficient coding skills might want to take it up

Sure.