I'm not going to retrace step by step the key points that Dom Robinson travels in his recent article titled "Reliable UDP (RUDP): The Next Big Streaming Protocol?" (http://go2sm.com/udp), but I do want to point out several highlights.
Third, the concept of reliable UDP has been around for quite some time and can be accomplished with a number of open source tools, but there are also a number of commercial licensees that offer tools based on RUDP.
Your mileage may vary if you want to tinker under the hood of a freeware application such as UDP Data Transfer, or you may just want to reach out to a vendor in the RUDP space.
Indeed, RDP appears to have been eclipsed in the late 1990s by the Reliable UDP Protocol (RUDP; http://go2sm.com/reliable), and both Cisco and Microsoft have released RUDP versions of their own within their stacks for specific tasks.
One way to think about how RUDP types of transport work is to use a basic model where all the data is sent in UDP format, and each missing packet is indexed.