EMQX
With over 16,500 GitHub stars and a track record powering connected vehicle fleets, smart city sensor networks, and industrial IoT deployments, EMQX is the MQTT messaging platform engineered to handle 100 million concurrent device connections in a single cluster while processing millions of messages per second with sub-millisecond latency. The protocol stack supports MQTT 5.0, 3.1.1, and 3.1 with full QoS 0/1/2 support, shared subscriptions, retained messages, and will messages, plus MQTT over QUIC for faster connection setup, reduced head-of-line blocking, and seamless connection migration on mobile networks. The gateway framework extends connectivity to MQTT-SN, CoAP, LwM2M, STOMP, and ExProto for bridging legacy industrial protocols. The SQL-based rule engine processes and transforms messages in real time with over 50 pre-built integrations including Kafka, PostgreSQL, MySQL, MongoDB, InfluxDB, TimescaleDB, ClickHouse, Redis, AWS Kinesis, GCP Pub/Sub, and Azure Event Hubs. The visual Flow Designer creates data processing pipelines without code. Built on Erlang/OTP with a masterless distributed architecture using Mria for state replication, the cluster separates Core nodes for data consistency and Replicant nodes for client-handling workloads. Authentication supports username/password, JWT, PSK, X.509 certificates, and LDAP with configurable ACL rules. The built-in dashboard provides real-time monitoring of connections, subscriptions, topics, message rates, and cluster health. Deployment runs via Docker, Kubernetes with the EMQX Operator, or native packages. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. BSL 1.1 licensed.
Eclipse Hono
Eclipse Hono is an IoT connectivity platform that sits between device fleets and business applications, accepting connections over MQTT, HTTP, AMQP 1.0, and CoAP adapters and normalizing everything into uniform telemetry and event streams. Devices authenticate against a central registry of tenants and credentials, with X.509 client certificates, pre-shared keys, or automatic provisioning for zero-touch onboarding. Applications consume normalized data from Apache Kafka or an AMQP 1.0 messaging network, choosing per tenant which backbone carries its traffic, and send commands back down to devices through the same platform with delivery feedback. Resource limits cap how much data each tenant's devices may move, keeping one noisy fleet from crowding out the rest, while metrics and tracing follow every message hop. The 2.7 release adds preliminary MQTT 5 support with corrected connect reason codes, message tracing logs, and a hardened JDBC device registry backed by PostgreSQL for production tenant and credential management. Protocol adapters scale horizontally as stateless services, so capacity grows by adding instances behind a load balancer. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. EPL-2.0 licensed.