run backup when internet is available

Hi Guys
I need to run a backup of 5 tables in my local database and update the information of the tables in my online database, now internet connection is limited, so i need to some how make a windows service to check if the internet is up and running, and if it is, then perform my backup and start updating my online database.
Now does anybody know how to make a windows service to check if your internet is up or down? if it is then start the backup.
And also, whats the best pratcice to perform the tasks above?
For now i just need an example to get the windows service to some how magically detect if theres internet or not.

Thanks guys

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