How to make register key to secure your own software

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Hi,Sir

I have been working for several months on a software and now it is
finished.
I have a problem now and it is this:
As soon as I give the software to some customers, the
software will be copied illegally and I don't want this happen.
Now I wonder if anyone could help me on how to create a lock or a
serial number for the software.
I want my software to generate a code based on the hardware used and
then when the customer enters that code in my web site, the web site
gives a valid serial number which activates the software (or something
like that).

So please teach me

How can I create serial no. or code ?
and
Method that my software to generate a code based on the hardware used and
then when the customer enters that code in my web site, the web site
gives a valid serial number which activates the software

please give me details with coding in secure language so i can make my activation kit.
my email Id is : dksir1011@gmail.com

Thanks