Question: Shell commands via telnet

[isavitsky]

Is there an easy way to redirect standard output to an open gnrc_tcp socket?
I started copying the shell functions I need (_netif_list() etc…) into my telnet shell application but maybe I'm missing a better way to reuse already existing shell code.

Thanks,
Ivan

[chrysn]

As far as I know there is none at the moment. stdio currently goes to UART (possibly wrapped when Ethernet-over-Serial (ETHOS) is active), the debugger (RTT) or USB serial once #11085 is merged, and all of them provide independent implementations of stdio_init, stdio_read and stdio_write.

(Apart from this telnet approach, there are different approaches circulating around how to best expose shell-like functionality over the network (a mail on the -devel list mentions #10624 and #9538; #7429 is related as well), but they go more in the direction of more abstract interactions rather than exposing the shell character by character.)

[isavitsky]

Thank you!
I think I will take a different approach into that.

Ivan

[benemorius]

I did the same thing and found that there's an easy way but there's no way that isn't a hack.

So far the best way I found was to hack the scheduler to change stdin and stdout depending on which thread is running. You can see what I did here: 54e73f1

The telnet server that uses this hack is here: 16cd537.

For me it's been working well in practice.

[isavitsky]

Thanks for the example with stdio hack!
I'm not yet decided whether I need all the shell stuff for my task or better to implement only the limited subset via API.

[jcarrano]

@HendrikVE was successful in exposing the shell via bluetooth- I believe he implemented stdio over bluetooth (which would mean it is no longer available via UART).

[HendrikVE]

@jcarrano Yes, i implemented a new stdio_nimble module for this purpose, which replaces the stdio_uart module. UART and bluetooth can be used in parallel btw (UART could also be disabled by a flag). At the end the shell simply uses my stdio module and shell output/input is delivered via bluetooth. No modification on the shell is needed.
@isavitsky You can get some inspiration by my PR #12012. You could implement your module the same way, it is important to declare your dependencies in RIOT's Makefile.dep, so that the buildsystem wont include a second stdio module.

[miri64]

@isavitsky is your question satisfied or do you want to open a feature request for telnet?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you want me to ignore this issue, please mark it with the "State: don't stale" label. Thank you for your contributions.

[chrysn]

Just for further reference: A full telnet server is now provided, see #16723 for details.