PubSubRT - an industrial pub/sub server

What is PSRT

PSRT is pub-sub protocol, optimized for industrial needs: low latency, slow channels and large payloads.

Why not MQTT?

We love MQTT. And we use MQTT a lot. There are cases where MQTT ideally fits requirements. However, for some it does not satisfy our speed and reliability needs and produces additional overhead. That is why we invented PSRT.

What is the difference?

• PSRT is the protocol, optimized for large (65K+) messages
• No QoS - all messages are always delivered to subscribers only once, so consider it has QoS=2 if using MQTT measurements
• No retain topics. Retains usually require disk writes, which produce additional overhead
• No OP-ACK loops. All control operations are fast, synchronous and atomic
• Two TCP sockets: one for control ops and the second one for incoming messages. This makes clients a bit more complicated, but allows to process incoming messages without additional overhead. Additionally, with two sockets control op acknowledgements and incoming message data can be mixed, which is important when large messages are processed on slow channels
• Devices and nodes, which do not need subscriptions, can use either a single TCP control socket or work without connection established, using UDP datagrams with or without acknowledge from the server
• PSRT is almost 100% logically compatible with MQTT, so software can be switched to it and vice-versa with only a couple of lines of code

About the repository

This repository contains PubSubRT server, implementing PSRT (open-source version without the cluster module), command-line client and Rust client library.

Other repositories:

• psrt-py - Python client library (sync)

Protocol specifications

https://github.com/alttch/psrt/blob/main/proto.md