Open an elevated command prompt then enter

query session

• Turn on File and Printer Sharing

Open a command prompt window and enter

msg * /server:<REMOTE NETBIOS HOSTNAME OR IP ADDRESS> "<insert text message>"

The asterisk (*) means all user sessions on specified server. This is helpful if you don’t know which user to specify and just want to reach any user on the remote host.

Full Syntax:

C:\WINDOWS\system32>msg /?
Send a message to a user.

MSG {username | sessionname | sessionid | @filename | *}
[/SERVER:servername] [/TIME:seconds] [/V] [/W] [message]

username Identifies the specified username.
sessionname The name of the session.
sessionid The ID of the session.
@filename Identifies a file containing a list of usernames,
sessionnames, and sessionids to send the message to.

* Send message to all sessions on specified server.
/SERVER:servername server to contact (default is current).
/TIME:seconds Time delay to wait for receiver to acknowledge msg.
/V Display information about actions being performed.
/W Wait for response from user, useful with /V.
message Message to send. If none specified, prompts for it
or reads from stdin.