AndroidAsync
Asynchronous socket, http(s) (client+server) and websocket library
...The library is based on Java NIO rather than a thread-heavy model, which makes it suitable for event-driven network communication. It is intended for developers who need direct protocol-level control instead of a higher-level request wrapper. The project also serves as the foundation for Ion, the author’s higher-level Android networking and image loading library. AndroidAsync is most useful for Android developers building custom networking layers, servers, streaming behavior, or WebSocket-based features.