Appia is an open source layered communication toolkit implemented in Java

Java (programming language)

Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...

, and licensed under the Apache License, version 2.0

Apache License

The Apache License is a copyfree free software license authored by the Apache Software Foundation . The Apache License requires preservation of the copyright notice and disclaimer....

. It was born in the University of Lisbon, Portugal

Portugal

Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, by the DIALNP research group that is hosted in the LaSIGE

LaSIGE

LaSIGE is a research unit of the Computer Science department of the Faculty of Sciences of the University of Lisbon, located at the Faculty's C6 building.-Research Lines:LaSIGE's research activities are organized around different topics, promoting research, training and...

 research unit. This framework

Software framework

In computer programming, a software framework is an abstraction in which software providing generic functionality can be selectively changed by user code, thus providing application specific software...

 provides extended configuration and programming possibilities.

Components

Appia is composed by a core that is used to compose protocols, and a set of protocols that provide group communication, ordering guaranties, atomic broadcast, among other properties.

Core

The Appia core offers a clean way for the application to express inter-channel constraints. This feature is obtained as an extension to the functionality provided by current systems. Thus, Appia retains a flexible and modular design that allows communication stacks to be composed and reconfigured in run-time.

Protocols

The existing protocols include interface with TCP

Transmission Control Protocol

The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

 and UDP

User Datagram Protocol

The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

 sockets

Internet socket

In computer networking, an Internet socket or network socket is an endpoint of a bidirectional inter-process communication flow across an Internet Protocol-based computer network, such as the Internet....

, virtual synchrony

Virtual synchrony

Virtual synchrony is an interprocess messaging passing technology. Virtual synchrony systems allow programs running in a network to organize themselves into process groups, and to send messages to groups...

, several implementations of total order

Total order

In set theory, a total order, linear order, simple order, or ordering is a binary relation on some set X. The relation is transitive, antisymmetric, and total...

, causal order, among others.