This is test.mosquitto.org. It hosts a publicly available Mosquitto MQTT server/broker. MQTT is a very lightweight protocol that uses a publish/subscribe model. This makes it suitable for "machine to machine" messaging such as with low power sensors or mobile devices.
The server listens on the following ports:
The encrypted ports support TLS v1.2, v1.1 or v1.0 with x509 certificates and require client support to connect. In all cases you should use the certificate authority file (mosquitto.org.crt (PEM format), or mosquitto.org.der (DER format)) to verify the server connection. Port 8884 requires clients to provide a certificate to authenticate their connection. It is now possible to generate your own certificate.
You are free to use it for any application, but please do not abuse or rely upon it for anything of importance. You should also build your client to cope with the broker restarting.
If you have the mosquitto clients installed try:
Please don't publish anything sensitive, anybody could be listening.
This server is provided as a service for the community to do testing, but it is also extremely useful for testing the server. This means that it will often be running unreleased or experimental code and may not be as stable as you might hope. It may also be slow - the broker often runs under valgrind or perf. Finally, not all of the features may be available all of the time, depending on what testing is being done. In particular, websockets and TLS support are the most likely to be unavailable.
In general you can expect the server to be up and to be stable though.
If you do publish things to this server on a regular basis, please get in touch to satisfy my curiosity - there are lots of topics that look interesting but I know nothing about. I'm ral on the freenode #mqtt irc channel, or see the mosquitto source for contact details..