ZeroMQ

ZeroMQ (also spelled 0MQ or ZMQ) is a high-performance, asynchronous messaging library designed for building distributed and concurrent applications. Originally created by iMatix Corporation (Pieter Hintjens and Martin Sustrik) in 2007, ZeroMQ provides a message queue abstraction without a dedicated broker, acting as a networking library that extends standard socket semantics with message-oriented patterns. With over 9,800 stars as of 2026, ZeroMQ is used by major financial institutions (JP Morgan, Bank of America), scientific computing projects (CERN LHC), and technology companies for high-throughput, low-latency messaging. The library provides several messaging patterns: request-reply (synchronous client-server with REQ/REP sockets), publish-subscribe (PUB/SUB sockets with topic-based filtering via prefix matching), pipeline (PUSH/PULL sockets for producer-consumer workloads and task distribution), exclusive pair (PAIR sockets for bidirectional 1:1 connections), and router-dealer (ROUTER/DEALER sockets for custom broker topologies and load balancing). Key features include: zero-broker architecture (peers connect directly, no central server needed, though one can be built using ROUTER/DEALER), transport options including TCP (tcp://), in-process (inproc://), inter-thread via IPC (ipc:// for Unix domain sockets), PGM (Pragmatic General Multicast for reliable multicast), and NORM, automatic reconnection with exponential backoff, message batching for throughput optimization (up to millions of messages per second), multipart messages (sending and receiving messages as a sequence of frames), socket type composition for complex topologies, CZMQ high-level C binding with actor pattern, and language bindings for over 40 languages including Python (pyzmq), Go (zmq4), Rust (zmq), Java (jeromq), Node.js, C#, Ruby, Haskell, and Erlang. As of 2026, ZeroMQ version 4.3.5 is maintained by the ZeroMQ community.