You can try this in your school or college systems(it should be networked systems).
Get the ip address of your friend's system.
if you are using college or school system,then ip address will be in particular range.
copy the following Batch code in notepad:
set /p n=IPAddress:
set /p m=Message:
net send %n% %m%
Save the file with .bat extension(For Eg: message.bat)
Open command prompt and navigate to that batch file location.
open the file in notepad.
If you don't know how to move to that path,simply drog and drop in cmd.Then hit enter.
Now it will ask you for the IPAddress.
Enter the IP address which you want to send message.
Now it will ask you for the message.
Enter and hit enter
The user with whom you connecting system's cmd should be opened in order to receive.
What is next? Comment Here! If the above method not working for you. Then comment what you did and What it showing. Or is it working perfectly ?then share your experience with us