# knolleary/pubsubclient

A client library for the Arduino Ethernet Shield that provides support for MQTT.

Repository: https://github.com/knolleary/pubsubclient
Canonical: https://ross.abutalabs.com/products/pubsubclient
Homepage: http://pubsubclient.knolleary.net/
Language: C++
License: MIT
License Family: permissive
Last push: 2026-06-10T11:54:58+00:00

## Health v2 (maintenance only)
Score: 62/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 86, release rhythm 8, longevity 100
- inputs: {"age_days": 6421, "days_push": 84, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 4014, forks 1503 (observed 2026-08-28T04:08:32.379825+00:00)

## What it is
PubSubClient is an Arduino C++ client library providing simple MQTT publish/subscribe messaging over the Arduino Ethernet Client API. It works with Ethernet/WiFi shields, ESP8266, and ESP32 boards, but the author has explicitly declared it unmaintained.

## Use cases
- connect an Arduino or ESP32 to an MQTT broker
- publish sensor readings over MQTT from ESP8266
- subscribe to MQTT topics on embedded hardware
- send IoT telemetry with publish/subscribe messaging
- MQTT client library for Arduino Ethernet Shield

## When to choose
- you need a tiny, simple MQTT client for a legacy Arduino project already using it
- your messages are small (256-byte default limit) and QoS 0 publishing suffices

## When to avoid
- starting a new project - the author urges using an actively maintained alternative
- you need QoS 2 or large message payloads
- you need MQTT 5 features

## Facets
- artifact type: library
- maturity: abandoned
- function: message-queue, http-client, iot
- domain: iot, embedded-systems
- platform: embedded, iot, cpp
- tags: mqtt, arduino, esp8266, esp32, publish-subscribe, unmaintained, messaging

## Member repositories
- knolleary/pubsubclient (main) score 62

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:32.379825+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:24:00.043298+00:00, confidence not recorded.
  - readme: https://github.com/knolleary/pubsubclient (fetched 2026-08-28T04:08:32.379825+00:00, sha 5e75a06137f5)
  - homepage: http://pubsubclient.knolleary.net/ (fetched 2026-08-29T09:16:49.187667+00:00, sha 14023b09d5f0)
  - site_page: http://pubsubclient.knolleary.net/api (fetched 2026-08-29T09:16:49.196794+00:00, sha f8df371efdb7)
  - site_page: http://pubsubclient.knolleary.net/api.html (fetched 2026-08-29T09:16:49.198997+00:00, sha f8df371efdb7)
- Data as of 2026-08-30T08:39:29.467469+00:00.