net send

net send

Sends a message to users or computers on the network.

 net send {   name   *  /domain[:   name   ]  /users}   message

name

Sends the message to a specific recipient, which can be:

*

Broadcasts the message to all registered NetBIOS names in the domain or workgroup

/domain[:name]

Broadcasts the message to all names in the local domain or a specified domain

/users

Sends the message to all users connected to the server

message

Is the actual message sent (no quotes required)

Send the message "Save your workrebooting in 5 minutes" to all users who have open sessions with the server:

  net send /users Save your work--rebooting in 5 minutes

In order for a user to receive messages, the Messenger service must be running.
Use quotation marks for computer names or usernames that have embedded spaces in them.
Messages can be up to 128 characters in length.
The message queue, which temporarily stores messages for the Messenger service, can store a maximum of only six messages; any further messages are ignored if the previous ones aren't acknowledged .
net send * is the same as net send /domain .
Broadcast messages ( * and /domain options) are sent over all network protocols. For example, if you have both TCP/IP and NWLink installed, messages will appear twice on receiving machines. Messages sent to specific recipients are received only once, however.
Broadcast messages are received only on the local subnet unless routers are specifically configured to forward NetBIOS Name Query packets.
Messages sent using the /user option are sent to each session established with the server. If a user has three sessions open with the server, the message will be received three times.