如何判断连接是否已计量？

I wrote a program that monitors an IMAP email account. It runs on a schedule, on a laptop that I travel with. Sometimes it runs when my internet connection is through my mobile device, which has a metered connection (that is, I pay by the GB), and I don't want it to, because it uses a lot of bandwidth, and it can wait until bandwidth is free.I wrote a program that monitors an IMAP email a