You can try to use the following API test tool (you probably need to use Firefox or any browser that does NOT force https. Chrome, for example, will force using https, so try a different browser if that is the case):
http://raysfiles.com/os/TestOSAPI.html
type in your OpenSprinkler’s IP address, port number, device password, and select Json Log (jl) API to test. See what’s the raw log data output. If it doesn’t work, you can copy the HTTP command generated by the test tool and paste that into a browser.