EventMachine implements a fast, single-threaded engine for arbitrary network communications. It's extremely easy to use in Ruby. EventMachine wraps all interactions with IP sockets, allowing programs to concentrate on the implementation of network protocols. It can be used to create both network servers and clients. To create a server or client, a Ruby program only needs to specify the IP address and port, and provide a Module that implements the communications protocol. Implementations of several standard network protocols are provided with the package, primarily to serve as examples. The real goal of EventMachine is to enable programs to easily interface with other programs using TCP/IP, especially if custom protocols are required.

Modern concurrency tools including agents, futures, promises, thread pools, actors, supervisors, and more. Inspired by Erlang, Clojure, Go, JavaScript, actors, and classic concurrency patterns.

Celluloid enables people to build concurrent programs out of concurrent objects just as easily as they build sequential programs out of sequential objects

Cool.io provides a high performance event framework for Ruby which uses the libev C library

A Ruby gem for performing work in background threads.

Dataflow concurrency for Ruby (inspired by the Oz language)

Actors based concurrency library for Ruby.

A lightweight, extensible asynchronous event routing framework in Ruby.