Comment # 1 on bug 983900 from Wolfgang Bauer

(In reply to Cristiano Guadagnino from comment #0)

> Also, I lost all bookmarks and the settings of KRDC's toolbar.

krdc has been ported to KDE Frameworks5, which uses different locations for 
config and data files.
But the automatic migration in krdc is broken, see 
https://bugs.kde.org/show_bug.cgi?id=361823

You can copy the bookmarks file manually from ~/.kde4/share/apps/krdc/ to 
~/.local/share/krdc/ to get them back.

Will be fixed in 16.04.3.

> The symptom is that if I enter the address of an RDP host, KRDC prompts me
> for the user, then (apparently) attempts to connect and then it suddenly
> returns to the "new connection" screen, without any error or message
> whatsoever.

Hm, I saw a similar problem on one system here when trying to reproduce your
problem by connecting via RDP to a VirtualBox VM running on the same host (I
did get an error dialog though that krdc was unable to connect), but on another
one it worked fine.
After copying over the bookmarks from the KDE4 version it worked on the first
system too, so in my case it was somehow related to the incomplete migration.

So please try this as well (see above), or try on a fresh user account, and see
if it works then.

I am on 13.2 though (using KDE:Frameworks5 and KDE:Applications).

> I tried to start KRDC from the command line to see if it sent some message 
to
> the console, but all I got was this, just before the error:
>
>  KBookmarkMenu::slotBookmarksChanged groupAddress:  "/0"

That's unrelated debug output.
I get that too, also when everything works.

> Another strange thing: if I enter "krdc -v" at the command line, this is
> what I get:
> 
>   cristiano@xmper8q3:~> krdc -v
>   krdc ��

krdc sets an integer version number instead of a string, you'll see this in 
the "About" dialog too.
But that is harmless and also unrelated.
I submitted a fix for that upstream already though, will be fine in 16.04.3 as
well...
https://quickgit.kde.org/?p=krdc.git&a=commit&h=c6fdda25fe1903999268716a5dcbe748f11c4dbd