The UPC protocol is the message format used by Union clients to communicate with the Union server.
The UPC protocol specification is published publicly to allow developers to create Union clients in any language.
Developers working with most Union Platform client frameworks, such as Reactor, do not need any direct knowledge of the UPC protocol. The protocol is typically used internally by client SDKs, not directly by application developers. An understanding of UPC is required only by developers who wish to create a custom client SDK for a new language, or who wish to communicate directly with Union using raw UPC messages.