How to broadcast a message in windows:
The service used for this is called messenger. you need to make sure the service is up and ready. The command that is used is net send
Step1) run services.msc
Setep2) look for messenger service and see if it is started
Step3) go to command prompt
Step4) run this command to broadcast to all:
net send * "Hello"
Note that this broadcast will be sent to all even if your messenger service is disabled.
Step5) Send message to a specific IP address:
net send 192.168.1.168 "hello from here"
At this point a message will be sent to the destination pc