Perhaps you did not read my reply carefully. There is NO such server already available in ns-3.
To create a server, you create a node and install an application.
You need to define how that application will operate.
For example you said you want to store some information.
Where do you want to store it?
Does it have to be a file or local storage is enough?
How is that information obtained?
What is it's format? What does it represent?
...
All these questions are NOT ns-3 specific. They are your design.
After you have a clear design, fully functional on paper, you can come back and ask specific question on how to implement parts of that design.
Most probably, we will refer you back to the ns-3 documentation, so study that before asking a question.
Regards,
K