There is a WinPopUp messenger in the local network I am member of. I would
like to use it too. I have installed linpopup for that purpose but when I try
to send anyone a message I constantly see an error, that connection failed.
Then I found this feature in smbclient itself. For example:

$ echo "Letters from Earth" | smbclient -M SWARG
Connection to SWARG failed

And of course the message is not delivered. Anyway, 'smbclient -L SWARG' works
fine. I know SWARG is controlled under Win32. I found a machine with Linux and
my messages reach it OK!? Sure with an appropriate configuring on its side (for
it could receive messages).

Can I partake WinPopUp chat somehow?

There are 2 projects doing this, LinPopUp and LinPopUp-2

Thank you for link.

But LinPopUp-2 is a front-end for "smbclient -M". This command does not work
for me too, hence LinPopUp-2 cannot help me.