Wire Protocol refers to a way of getting data from point-to-point: A Wire Protocol is needed if more than one application has to interoperate. It generally refers to protocols higher than the physical layer. In contrast to transport protocols at the transport level (like Transmission Control Protocol (TCP) or User Datagram Protocol (UDP)), the term “wire protocol” is used to describe a common way to represent information at the Application Level of the Open Systems Interconnection (OSI) Model. It refers only to a common Application Layer protocol and not to a common object semantic[clarification needed] of the applications. Such a representation at application level needs a common XML Information Set (XML Infoset) and a data binding (using e.g. a common encoding scheme like XML Schema Definition (XSD)).
It generally refers to higher layers, including Ethernet and ATM (layer 2) and even higher layer distributed object protocols such as Simple Object Access Protocol (SOAP), CORBA or RMI.
The Wire Protocol may be either text-based or a binary protocol. Although an important architectural decision, this is a separate matter from the distinction between Wire Protocols and programmatic Application Programming Interfaces (APIs).
Source: Wire Protocol