[keycloak-user] Missing form parameter: grant_type while using the REST API

Hello, I'm trying to get an access token from my Keycloak Server. I'm sending a post request to http://localhost:12345/auth/realms/testRealm/protocol/openid-connect/toke... with additional header "Content-type: application/x-www-form-urlencoded; charset=UTF-8". The response I get is: HTTP/1.1 400 Bad Request Connection: keep-alive Cache-Control: no-store Pragma: no-cache Content-Type: application/json Content-Length: 84 Date: Tue, 28 May 2019 10:14:08 GMT {"error":"invalid_request","error_description":"Missing form parameter: grant_type"} Do you have any idea what is the cause of the problem? Did I miss something to configure? The administration console works well. I'm using Keycloak 6.0.1 as standalone. I had to change the port because the default port is not free on my host. Could it be, that I missed something there? Thank you!