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Eclipse Paho MQTT C

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connect C applications to MQTT 5.0/3.1.1 brokers through synchronous or asynchronous APIs over TCP, TLS, WebSockets, and Unix sockets

OSS scale score 247.5OSS health 82Update pace 0 commits/30d
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Stars
2,373
Primary language
C
License
EPL-2.0 OR BSD-3-Clause
Repository last updated
Sep 9, 2026
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Overview

Eclipse Paho MQTT C is a client library for connecting C applications to MQTT brokers. It provides the classic synchronous MQTTClient API and asynchronous MQTTAsync API with MQTT 5.0/3.1.1 support and transport options including TCP, SSL/TLS, WebSockets, and Unix-domain sockets.

Features and best fit

Based on official documentation; not hands-on tested · Content checked:

Key features

Choose synchronous or asynchronous APIs for the application architecture

The paho-mqtt3c family provides the classic synchronous API while paho-mqtt3a provides the asynchronous API, allowing the client model to match application threading and event flow.

Sources: [1]

Connect over TCP, TLS, WebSockets, or Unix-domain sockets

URI schemes and build options support plain TCP, SSL/TLS, secure and insecure WebSockets, and Unix-domain sockets on supported systems.

Sources: [1]

Link explicit CMake targets for shared/static and TLS variants

The CMake package exports targets for async/sync, TLS/non-TLS, and shared/static variants so applications can state the intended dependency precisely.

Sources: [1][2]

Best fit

Fits native C applications on Windows, Linux, and macOS that need MQTT connectivity

It is useful for native applications, gateways, and device-side software that need MQTT integrated into an existing event loop or threading architecture.

Sources: [1]

Before adoption

TLS requires both a TLS-enabled build and connection SSL options

Secure transports require building with PAHO_WITH_SSL=TRUE and supplying SSL options when connecting to the broker.

Sources: [1]

The test suite expects an MQTT broker

CMake tests use a broker, defaulting to localhost. Separate compile validation from broker integration tests and explicitly provision an isolated test broker in CI.

Sources: [1]

1.3.16 enables TCP_NODELAY by default

Version 1.3.16 includes connect-latency improvements, enables TCP_NODELAY by default, and raises the minimum CMake version to 3.12, so latency-sensitive deployments should account for the network-behavior change.

Sources: [3][2]

Official sources

  1. [1]Paho MQTT C 1.3.16 README(2026-10-04)
  2. [2]Paho MQTT C 1.3.16 CMake configuration(2026-10-04)
  3. [3]Paho MQTT C 1.3.16 release(2026-10-04)
  4. [4]Paho declared project licenses(2026-10-04)
Supplemental curator note

The library is built in synchronous/asynchronous and TLS/non-TLS variants. Choose the link target and transport requirements explicitly; TLS builds require PAHO_WITH_SSL=TRUE and connection-time SSL options. Version 1.3.16 also enables TCP_NODELAY by default and includes connect-latency improvements.

Try it in 3 steps

  1. 1

    Fetch the Paho MQTT C 1.3.16 source

    Pin the source checkout to stable v1.3.16.

    git clone --depth 1 --branch v1.3.16 https://github.com/eclipse-paho/paho.mqtt.c.git paho-mqtt-c-1.3.16
  2. 2

    Configure a minimal CMake build without TLS or tests

    Keep the validation local by avoiding OpenSSL and broker-dependent tests.

    cmake -S paho-mqtt-c-1.3.16 -B paho-mqtt-c-1.3.16/build -DPAHO_WITH_SSL=OFF -DPAHO_ENABLE_TESTING=OFF -DPAHO_BUILD_SAMPLES=OFF
  3. 3

    Build the synchronous client-library target

    Build the classic synchronous shared-library target to validate the C compiler and CMake environment.

    cmake --build paho-mqtt-c-1.3.16/build --target paho-mqtt3c
Check the official README

Growth

Growth trends · Last 30 days

2,373 Stars

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Development activity

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Commits (last 30 days)
0
Open PRs
58

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GitHub data

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GitHub Topics

  • eclipseiot
  • mqtt
  • iot
  • internet-of-things
  • eclipse-paho
Stars
2,373
Forks
1,192
Watchers
111
Open issues
169
Contributors
96
Owner type
Organization
Primary language
C
Repository last updated
Sep 9, 2026
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