What I found to work on a 2012 server.
Make sure "Allow remote connections to this computer" is checked.
Uncheck "Allow connections only from computers running Remote Desktop with Network Level Authentication (recommended)"
Not sure if rdesktop can (or is being developed to) work with that type of authentication. Hopefully you have privs to make this change.
From: Marcelo Ganin [mailto:marceloganin@...]
Sent: Tuesday, May 21, 2013 9:05 AM
Subject: [rdesktop-users] Conect windows sever 2012
Error when accessing a windows server 2012. rdesktop xxx.xx.xx.xx
ERROR: recv: Connection reset by remote machine.
If I try to connect to a windows server 2008 connects seamlessly.