delphi - Using Indy to retrieve Revcontent OAuth Token -

i trying use indy retrieve revcontent oauth token according this page. here code:

procedure tform2.button1click(sender: tobject); var   idssliohandlersocket1: tidssliohandlersocketopenssl;   idhttp:tidhttp;   params: tstringlist; begin   idhttp:=tidhttp.create(self);   idssliohandlersocket1 := tidssliohandlersocketopenssl.create(nil);   idssliohandlersocket1 begin     ssloptions.method := sslvsslv23;     ssloptions.sslversions := [sslvsslv23];   end;    params := tstringlist.create;   params.add('clientid=xxyyzz');   params.add('client_secret=xxyyzzxxyyzzxxyyzzxxyyzzxxyyzzxxyyzz');   params.add('grant_type=client_credentials');   idhttp begin     iohandler := idssliohandlersocket1;     request.contenttype := 'application/x-www-form-urlencoded';   end;   showmessage(idhttp.post('https://api.revcontent.io/oauth/token',params)); end; 

but whenever run 400 bad request error. doing wrong?

use client_id, not clientid.
not use ssl3, site supports tls1.
not set contenttype.
use try/except around post catch exception , full error message (e eidhttpprotocolexception).errormessage