It basically uses TCP. Raw unreliable UDP is also supported on Ruby and Java. TCP or UDP will be enough choices for most of applications. Practically, MessagePa

It basically uses TCP. Raw unreliable UDP is also supported on Ruby and Java. TCP or UDP will be enough choices for most of applications. Practically, MessagePack-RPC mainly focuses on cross-language communication, like Ruby frontend <-> C++ backend. So portability is rather important.