Get started
Follow this guide to compile the synchronous sample client and verify broker connectivity.
Before you begin
Make sure you have:
TrustCore SDK U6 or later (NanoMQTT is built in by default). To rebuild only NanoMQTT, run
./build.sh nanomqttfromprojects/mqtt_client/.A POSIX shell and a C11‑compatible tool‑chain.
(Optional) A system CA bundle. On most Linux distributions this is
/etc/ssl/certs/ca-bundle.crt(or/etc/ssl/certs/ca-certificates.crt). If the file is missing or outdated, TLS verification will fail.Access to a public or private MQTT broker. The examples use broker.hivemq.com.
Build the sample client (with SSL)
./scripts/nanomqtt/mqtt_client/build_mqtt_client.sh --ssl
The script creates mqtt_client_sample in mocn-mss/bin/.
cd mocn-mss # run commands from here
Quick publish/subscribe demo
Export a few helper variables:
export MQTT_SERVER=broker.hivemq.com # any MQTT‑5 capable broker export MQTT_PORT=1883 # TCP export MQTT_SSL_PORT=8883 # TLS
Start a subscriber (plain TCP)
./bin/mqtt_client_sample \
--mqtt_servername ${MQTT_SERVER:-broker.hivemq.com} \
--mqtt_port ${MQTT_PORT:-1883} \
--mqtt_sub_topic demo/topic \
--mqtt_clean_start
Tip
See Command-line reference for option details.
The client blocks, waiting for messages.
Publish a message over TLS
./bin/mqtt_client_sample \
--mqtt_servername ${MQTT_SERVER:-broker.hivemq.com} \
--mqtt_port ${MQTT_SSL_PORT:-8883} \
--mqtt_transport SSL \
--ssl_ca_file /etc/ssl/certs/ca-bundle.crt \
--mqtt_pub_topic demo/topic \
--mqtt_pub_message "Hello NanoMQTT" \
--mqtt_clean_start
Look for the expected subscriber output:
demo/topic Hello NanoMQTT
Caution
--ssl_allow_untrusted disables server‑certificate validation and is suitable only for ad‑hoc tests.