Can TCP be implemented via UDP?

Question

I had a strange idea. I heard of software which from my understanding uses UDP to transfer files decreasing the overhead found in TCP packets.

If my app requires TCP and

Answer 1

Yes, you can develop a protocol on UDP that simulates TCP. However, if you simulated TCP fully, it would technically have more overhead. Because TCP is implement as the packet and your simulated TCP is implemented in the body of the packet.

If you only need one or two features of TCP (such as basic ordering), then implementing it in UDP is useful.

Halo uses 2-3 (IIRC) UDP protocols that simulate different features of TCP, then full fledged TCP for initializing game-states. I Shot You First Networking, GDC publication

For example, in one case, they send 3 duplicate UDP packets to overcome packet loss.

If you control the software on both ends, and it is cost-effective to build your own protocol, then UDP can be versatile.