ZeroMQ

ZeroMQ (also spelled ØMQ, 0MQ or ZMQ) is an asynchronous messaging library, aimed at use in distributed or concurrent applications. It provides a message queue, but unlike message-oriented middleware, a ZeroMQ system can run without a dedicated message broker; the zero in the name is for zero broker. The library's API is designed to resemble Berkeley sockets. ZeroMQ is developed by a large community of contributors, founded by iMatix, which holds the domain name and trademarks. There are third-party bindings for many popular programming languages. The ZeroMQ API provides sockets (a kind of generalization over the traditional IP and Unix domain sockets), each of which can represent a many-to-many connection between endpoints. Operating with a message-wise granularity, they require that a messaging pattern be used, and are particularly optimized for that kind of pattern. The basic ZeroMQ patterns are: Request–reply Connects a set of clients to a set of services. This is a remote procedure call and task distribution pattern. Publish–subscribe Connects a set of publishers to a set of subscribers. This is a data distribution pattern. Push–pull (pipeline) Connects nodes in a fan-out / fan-in pattern that can have multiple steps, and loops. This is a parallel task distribution and collection pattern. Exclusive pair Connects two sockets in an exclusive pair. (This is an advanced low-level pattern for specific use cases.) Each pattern defines a particular network topology. Request-reply defines a so-called "service bus", publish-subscribe defines a "data distribution tree", and push-pull defines "parallelised pipeline". All the patterns are deliberately designed in such a way as to be infinitely scalable and thus usable on Internet scale. Any message through the socket is treated as an opaque blob of data. Delivery to a subscriber can be automatically filtered by the blob leading string. Available message transports include TCP, PGM (reliable multicast), inter-process communication (IPC) and inter-thread communication (ITC).