send commands to a remote screen console

[Marco Strullato]

Hi all, I have a problem with screen:

At first I execute "ssh address@hidden screen -d -m" to open and detach a console on a remote server. 
Then I want to execute a command into this console and I execute "ssh address@hidden screen -X ls". I get this answer: "Connection to server closed."

However I can log into this server (I set up pki ssh auth) to login with keys.

Suggestions?

I also use the -S flag to specity the session but it was unuseful.

What's wrong?

Thanks

Marco