If you are working on a PC and you want to send a message to your friend/colleague. Then you can use your PC to send any message and it is very simple and it does not require any software. For that, you should know the IP address or system name of the target system.
Now to send a message, open the command prompt of your system and type command
msg /server:172.16.16.110 * /TIME:60 "Your message here."
And on the target system, you will get message like -
Enjoy!!!
