thank you for reply. After waiting 20 minutes, message was changed into "error code: -32601 error message: Method not found" – user6894661 – 2017-09-21T03:48:12.573

That's because getinfo was removed. It's marked as deprecated with a warning in 0.15, but apparently you're running master (which will become 0.16, with getinfo removed). – Pieter Wuille – 2017-09-21T05:21:25.217

You should use getwalletinfo, getblockchaininfo, getpeerinfo, getnetworkinfo, ... to request more specific information. – Pieter Wuille – 2017-09-21T05:22:16.853

I tried these commands you showed then I got return! Thank you! – user6894661 – 2017-09-21T10:49:46.137