check user bandwidth

how do i check the bandwidth (download speed and pos开发者_开发知识库sible upload speed) of a user in vb.net or php that uses my app or visits my site resp?

thanks

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Basically, you test it. Check out SpeedTest.net for an example.

You download a file, and then upload it and measure the times.

Most of the online speed testers use flash for this purpose, so the user doesn't have to worry about browsing for a file to upload.