Pnxi

pnxi is a lightweight application‑level messaging protocol that facilitates secure, real‑time communication between distributed systems. Designed in 2016 by the OpenGrid consortium, pnxi targets environments with constrained bandwidth and limited processing resources, such as embedded devices, industrial instrumentation, and low‑power sensor networks. The protocol is formalized in a public specification released under the MIT license, allowing open community development and integration.

The pnxi message format is XML‑based but can be optionally compressed with DEFLATE to reduce payload size. Each message consists of a mandatory header, optional authentication token, and a payload section that can carry arbitrary binary or textual data. Authentication is achieved through a challenge‑response scheme that employs HMAC‑SHA256, giving the protocol resistance to replay attacks while keeping computational demands low. Message sequencing and acknowledgments are handled via lightweight sequence numbers embedded in the header, enabling flow control without heavy state management.

Implementation libraries are available for C, C++, Java, Python and Go, and pnxi is supported by popular IoT platforms such as Eclipse Hono, AWS IoT Greengrass, and Azure IoT Edge. The protocol has been adopted in several industrial use cases, including predictive maintenance of wind turbines, real‑time telemetry in autonomous ships, and secure firmware updates for consumer electronics. The pnxi community actively maintains a registry of interoperability examples and provides a set of test suites to validate conformance.

Future work outlined in the latest specification includes optional integration with WebAssembly modules for in‑band computation, and a draft specification for end‑to‑end encryption based on the Noise protocol framework. pnxi remains a relevant choice for developers seeking a balance between security, efficiency and ease of deployment in distributed computing environments.