zeroMQ

ZeroMQ is a high-performance asynchronous messaging library designed for scalable distributed and concurrent applications. It provides a socket-like API that abstracts underlying transport layers and enables various messaging patterns without requiring a separate broker. The core library, commonly used as libzmq, exposes a small set of socket types and a flexible framing model to support different topologies.

Socket types in ZeroMQ include PUB/SUB for publish-subscribe, REQ/REP for request-reply, DEALER/ROUTER for advanced routing, PUSH/PULL for load-balanced pipelines, and PAIR for simple one-to-one connections. These sockets can be combined to implement patterns such as publish-subscribe, request-reply, fan-out/fan-in, and pipelining. Messages are composed of frames, allowing multipart messages to be transmitted atomically across transports.

ZeroMQ transports include in-process (inproc), inter-process (ipc), TCP, and multicast options (PGM/EPGM). This transport independence enables applications to switch between local and networked communication with minimal code changes. The library emphasizes brokerless communication by default, with direct endpoints communicating through the library; brokers can be introduced for certain topologies via bridging or external components.

Binding availability is broad, with language bindings for many programming languages, making ZeroMQ suitable for polyglot architectures and rapid prototyping. It is widely used for building distributed systems, event buses, task queues, data streaming, and real-time messaging.

Originating in the mid-2000s, ZeroMQ was created by Pieter Hintjö at iMatix and has since evolved into a widely adopted open-source project. It remains a foundational tool for developers seeking fast, flexible messaging without a mandatory centralized broker.