C/C++ APIs for UDP protocol connection

[Mimmo DF]

HI All,
I've read that Memcached support both TCP/UDP protocol connection,
My testing system uses libmemcache (or apr-mamcache) like Apache module.
That APIs are developed exclusively for TCP protocol?
I don't need UDP protol connection, but I'm curious to know if there
are technicals reasons to use only TCP protocol on C/C++ APIs.

Thanks, Mimmo