Curl requests to Appium

Hi!
Previously used Appium version 1.4.13. During the running session on the Android device on the request:
curl -N http://localhost:4723/wd/hub/status
received the response:
{"status":0,"value":{"build":{"version":"1.4.13","revision":"c75d8adcb66a75818a542fe1891a34260c21f76a"}},"sessionId":"29b3c645-a825-404a-aded-d3c97717abad"}
Updated on the Appium 1.6.5. Now the same request get the response:
{"status":0,"value":{"build":{"version":"1.6.5","revision":null}},"sessionId":null}
It does not matter is now going session or not!

First of all, I’m interested in knowing the sessionId. Or some other pointer to the fact that the test session is currently running.
Perhaps there are other CURL requests to the Appium server? I would like to have a complete list of CURL requests to the Appium. Or maybe the requests have changed for the new version Appium 1.6.5?

Sorry for bad english.
Thank you all in advance!