Easiest way to cut off net access?

Okay my parents asked me if it would be possible to write a program that can limit the time frame during which the internet can be accessed from my sisters computers. I haven't done any type of real network programming in C++ (some in Java) and figured this would be a good project to get a little bit ahead of my classes and to not forget everything I learned over the summer. The problem is, as far as actually blocking the internet I don't know where to begin at all. I can make the interface and set it up for my parents to access the settings and change what times they can use the net but I don't know how to actually cut it off. I'm sure there are many ways I was just looking for any easy suggestions.
Thanks

Heres an easy way. Just run the command line programs below however you want (system("COMMAND") comes to mind).

This won't stop anyone who knows much about Windows from using the internet, but should stop anyone somewhat computer illiterate.

Simply run the command

Code:

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ipconfig /release_all

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to release all the network connections (disable the internet).

Code:

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ipconfig /renew_all

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to enable/reactivate all the network connections.

Thats the easiest way I can think of off the top of my head.

Thus,

Code:

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system("ipconfig /release_all");

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should disable it, etc.

Also, there is another command for Windows XP to stop network connections, the code is as follows:

Code:

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system("NET STOP NETWORK CONNECTIONS");

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You usualy have a pair of quotes surrounding Network connections, but of course, it wont work here.

Which means that the command probaly wont work either, however, you could to it this way:

Code:

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system("start net.bat");

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And then save the following code as net.bat in the programs folder, via Notepad:

Code:

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@echo off
net stop "network connections"
exit

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And then to start it back up, create a another batch file using net start instead of net stop, or use variables.

Of course, Crazy Norman's way is more efficient, and easier. ;)