POST JSON data with cURL
Set your content-type to application/json, header as POST and your data.
curl -H "Content-Type: application/json" -X POST -d '{"username":"john","password":"john@98365"}' http://localhost:3350/api/login
If you want to POST a JSON from a file..
curl -X POST -H "Content-Type: application/json" -d @credentials.json http://localhost:3350/api/login