A realtime distributed messaging platform

Apache RocketMQ is a cloud native messaging and streaming platform, making it simple to build event-driven applications.

High-Performance server for NATS.io, the cloud and edge native messaging system.

Apache Pulsar - distributed pub-sub messaging system

The most scalable open-source MQTT broker for IoT, IIoT, and connected vehicles

IM Chat ChatGPT

Open source RabbitMQ: core server and tier 1 (built-in) plugins

Instant messaging platform. Backend in Go. Clients: Swift iOS, Java Android, JS webapp, scriptable command line; chatbots

An elegant messages UI library for iOS

ZeroMQ core engine in C++, implements ZMTP/3.1

Scalable real-time messaging server in a language-agnostic way. Self-hosted alternative to Pubnub, Pusher, Ably. Set up once and forever.

Berty is a secure peer-to-peer messaging app that works with or without internet access, cellular data or trust in the network

Efficient reliable UDP unicast, UDP multicast, and IPC message transport

SimpleX - the first messaging network operating without user identifiers of any kind - 100% private by design! iOS, Android and desktop apps 📱!

Distributed Application Framework for .NET

Robust, Ubiquitous and Massively Scalable Messaging Platform (XMPP, MQTT, SIP Server)

A community-driven replacement for JSQMessagesViewController

Kafka implemented in Golang with built-in coordination (No ZK dep, single binary install, Cloud Native)

Apache Kafka® running on Kubernetes

qTox is a chat, voice, video, and file transfer IM client using the encrypted peer-to-peer Tox protocol.