New I/O for Ruby (nio4r): cross-platform asynchronous I/O primitives for
scalable network clients and servers.  Modeled after the Java NIO API, but
simplified for ease-of-use.

nio4r provides an abstract, cross-platform stateful I/O selector API for Ruby.
I/O selectors are the heart of "reactor"-based event loops, and monitor
multiple I/O objects for various types of readiness, e.g. ready for reading or
writing.