#  [](http://rubygems.org/gems/nio4r) [](https://github.com/socketry/nio4r/actions?query=workflow:nio4r) [](https://codeclimate.com/github/socketry/nio4r) [](https://coveralls.io/r/socketry/nio4r) [](http://www.rubydoc.info/gems/nio4r/2.2.0) **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. ## Projects using nio4r * [ActionCable]: Rails 5 WebSocket protocol, uses nio4r for a WebSocket server * [Celluloid]: Actor-based concurrency framework, uses nio4r for async I/O * [Async]: Asynchronous I/O framework for Ruby * [Puma]: Ruby/Rack web server built for concurrency [ActionCable]: https://rubygems.org/gems/actioncable [Celluloid]: https://github.com/celluloid/celluloid-io [Async]: https://github.com/socketry/async [Puma]: https://github.com/puma/puma ## Goals * Expose high-level interfaces for stateful IO selectors * Keep the API small to maximize both portability and performance across many different OSes and Ruby VMs * Provide inherently thread-safe facilities for working with IO objects ## Supported platforms * Ruby 2.4 * Ruby 2.5 * Ruby 2.6 * Ruby 2.7 * Ruby 3.0 * [JRuby](https://github.com/jruby/jruby) * [TruffleRuby](https://github.com/oracle/truffleruby) ## Supported backends * **libev**: MRI C extension targeting multiple native IO selector APIs (e.g epoll, kqueue) * **Java NIO**: JRuby extension which wraps the Java NIO subsystem * **Pure Ruby**: `Kernel.select`-based backend that should work on any Ruby interpreter ## Documentation [Please see the nio4r wiki](https://github.com/socketry/nio4r/wiki) for more detailed documentation and usage notes: * [Getting Started]: Introduction to nio4r's components * [Selectors]: monitor multiple `IO` objects for readiness events * [Monitors]: control interests and inspect readiness for specific `IO` objects * [Byte Buffers]: fixed-size native buffers for high-performance I/O [Getting Started]: https://github.com/socketry/nio4r/wiki/Getting-Started [Selectors]: https://github.com/socketry/nio4r/wiki/Selectors [Monitors]: https://github.com/socketry/nio4r/wiki/Monitors [Byte Buffers]: https://github.com/socketry/nio4r/wiki/Byte-Buffers See also: * [YARD API documentation](http://www.rubydoc.info/gems/nio4r/frames) ## Non-goals **nio4r** is not a full-featured event framework like [EventMachine] or [Cool.io]. Instead, nio4r is the sort of thing you might write a library like that on top of. nio4r provides a minimal API such that individual Ruby implementers may choose to produce optimized versions for their platform, without having to maintain a large codebase. [EventMachine]: https://github.com/eventmachine/eventmachine [Cool.io]: https://coolio.github.io/ ## Releases ### CRuby ``` rake clean rake release ``` ### JRuby You might need to delete `Gemfile.lock` before trying to `bundle install`. ``` rake clean rake compile rake release ``` ## License Released under the MIT license. Copyright, 2019, by Tony Arcieri. Copyright, 2019, by [Samuel G. D. Williams](http://www.codeotaku.com/samuel-williams). Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. ### libev Released under the BSD license. See [ext/libev/LICENSE] for details. Copyright, 2007-2019, by Marc Alexander Lehmann. [ext/libev/LICENSE]: https://github.com/socketry/nio4r/blob/master/ext/libev/LICENSE
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