Thank you for yr response.
Meteor is running on Linux.
It is solved!!!
There was an error (syntax) to the sending string!
I have also another question.
To a channel A are joined many clients. When a new client joins to a
channel for a first time, it receives all the messages stored for this
channel. That's fine, but when next time it joins the same channel must
not receive any of the old message, until a new one message comes up.
Have I to deploy a new functionality for this?
Thanks a lot