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Installing and configuring the Mosquitto MQTT broker

This post contains basic instructions on installing and configuring Mosquitto MQTT broker for application development.

Install Mosquitto

In a Docker container

docker run -it --name mosquitto1 -p 1883:1883 eclipse-mosquitto

Add --net=host if you want the container to use the same IP address as host—this is not supported in Docker for macOS and Windows.

To restart container later

docker start -ai mosquitto1

To edit config file exec command shell in container

docker exec -it mosquitto1 /bin/sh

Run vi

vi /mosquitto/config/mosquitto.conf

Install on Windows

Download and run installer available at https://mosquitto.org/download/. See that the option to install service is checked. Configuration file mosquitto.conf is located at C:\Program Files\mosquitto by default. You’ll need to restart the mosquitto service each time you edit the config file.

Install on macOS

With HomeBrew

brew install mosquitto

To run it


The default config file is located at /usr/local/opt/mosquitto/etc/mosquitto/mosquitto.conf.

Enable Persistence

In Docker container

persistence true
persistence_file mosquitto.db
persistence_location /mosquitto/data/

On Windows

persistence true
persistence_file mosquitto.db
persistence_location C:/Program Files/mosquitto/

Enable logging

Docker container logs to standard output.

On Windows

log_dest file C:/Program Files/mosquitto/mosquitto.log
log_type all

You may have to tweak file permissions to be able to view it.

Setup TLS 1.2

TLS 1.2 can be enabled using a self-signed certificate. You can generate one using OpenSSL or PowerShell.

To enable TLS 1.2 for default listener

cafile C:/Program Files/mosquitto/cacert.pem
certfile C:/Program Files/mosquitto/cert.crt
keyfile C:/Program Files/mosquitto/key.pem
tls_version tlsv1.2

cacert.pem bundles well known CA Root Certificates maintained by Mozilla, and is available in PEM format at https://curl.haxx.se/ca/cacert.pem. You can replace the contents of the file with just the root certificates you want to accept, but the file cannot be empty.

cert.crt needs to be in ASCII PEM format. Mosquitto on Windows does not accept line endings with a single carriage return as used by macOS. You’ll also need to add cert.crt to the Trusted Root Certification Authorities keystore used by any clients.

Setup username/password authentication

Create password file

mosquitto_passwd -c passwordfile user1

Add another user

mosquitto_passwd -c passwordfile user1

Disable anonymous access and specify password file

allow_anonymous false
password_file C:/Program Files/mosquitto/passwordfile

Perform access control

Create aclfile

# This only affects clients with username "user1".
user user1
topic foo/bar

user1 can only subscribe and publish to topic foo/bar.

Specify acl_file in configuration

acl_file C:/Program Files/mosquitto/aclfile

Setup listener for WebSocket

To configure a second listener for the WebSocket protocol over TLS 1.2

# listener port-number [ip address/host name]
listener 8443
protocol websockets
cafile C:/Program Files/mosquitto/cacert.pem
certfile C:/Program Files/mosquitto/cert.crt
keyfile C:/Program Files/mosquitto/key.pem

Configure a bridge

Run another Mosquitto instance using Docker, to act as the bridge

docker run -it --name bridge1 -p 1884:1883 eclipse-mosquitto

Configure mosquitto1 container to publish/subscribe messages on any topic to bridge1 container, with QoS Level 1

connection bridge1
topic # both 1

Adjust host IP address appropriately.