Latest on the Eclipse Paho Project

We recently announced the release of Eclipse Paho 1.4, which includes updates to the C, Python and Go client libraries. The embedded C and Java clients are delayed somewhat. The fact that we have a Paho project release may pass many people by because they only look at the activities of individual components. Paho is an unusual Eclipse project in that regard. I think the notion is useful however, if ‘only’ in practical terms, because these releases accomplish some Eclipse formalities which are worth the effort: IP log checking, Eclipse IoT and Foundation release reviews. A global Paho release saves the individual committers from having to do this separately and for each component.

The next release I’m tentatively thinking about for later this year or early next, with more MQTT V5 updates. So its schedule pretty much depends on when those updates are ready (C++, embedded C, Go, Python?).

We do have some work outstanding on the website, and it can always be improved. We’re always interested in ideas. Apart from the specific calls for help below, we are open and would appreciate help in any of the areas, especially if anyone is interested in becoming a committer. I wrote a another blog post with some more thoughts a while back.

C client

Recently I finally cut a the 1.3 release of the Paho C client which is notable for adding support for MQTT V5. It took longer than I had hoped to get to the point where I was happy to stamp the release tag on, which in hindsight is not that surprising as MQTT V5 support is the biggest addition to the client since it was originally created around around 10 years ago.

Obviously the amount of functionality needed in an MQTT client library is not infinite, and I’ve wondered when it would be basically complete, with no more new features needed by anyone. With the addition of support for MQTT V5, and also WebSockets courtesy of Keith Holman’s contribution, we’re closer than ever. But if you look at the outstanding list of enhancements we’re not quite there yet! We’re always interested in contributions, so if you are interested in fixing any of these issues, please do have a go.

Java

A similar story with the Java client and its support for MQTT V5, but we’re not quite there yet, as you can see from the outstanding issues. James, the maintainer for the Java client, has just moved jobs and is stretched for time. I’m working with him to resolve those final issues and make the release available as soon as we can. The basic support for MQTT V5 is ready, so you can go ahead and try it, it’s the tests and minor issues around the edge that we want to clean up.

Kamil’s mqtt-spy utility relies on the Java client, so I’m hoping that can move ahead soon.

Test Material

The Paho test material includes a (Python) broker which supports MQTT V5. I wrote it as an update to the existing broker so that we could use it for testing V5 client implementations. It supports TLS and WebSockets too, and is used by the C and Java clients in their CI tests.

C++

The C++ client is a layer over the C client, so now that is ready, I’m hoping Frank is good to start. In a recent email, Frank said that he aims to get V5 support in by the end of the year. I’m keeping my fingers crossed for that 🙂

Likewise with Frank’s Rust client, which is also based on the C. I expect V5 support will be added after the C++ client is done?

Python

Pierre has cut a new release of the Python client, 1.4. It doesn’t include MQTT V5 support, but I’ve created a PR with a start of that. I’m hoping we can see V5 support available by the end of the year too.

Embedded C

I started with V5 updates to this client library, and completed the implementation of V5 support in the MQTTPacket low level library. That was where I paused to turn my attention to the mainline C library. Now it’s the turn of the embedded library again. I also hope to work on the long intended threaded MQTTAsync, threaded embedded library.

Go

A service update 1.1.1 was delivered in March this year. Al has started developing MQTT V5 updates some time ago, using the Paho V5 Python broker for testing. I’m hoping we can see the fruits of his labour produce a V5 release in the near future.

C#

Unfortunately there haven’t been any regular updates to the C# client for quite a while. I’ve spoken to Paolo about the future, and he would like to see this project continue, but can’t necessarily devote much time to it. We did ask if anyone out there is interested, and had one offer which we’re waiting to see if that works out. If anyone else is interested in contributing to the C# client, do get in touch.

Ruby

The Ruby client is a recent contribution which we’re very happy to have on board. Another Pierre, Goudet, is responsible for it. It took a long time for the contribution to be accepted because of the IP questions that had to be resolved, and we appreciate the persistence of the contributors for working through that very much. I hope that we can get a first official Paho release soon.

JavaScript

We haven’t had a specific maintainer for the JavaScript client for a while. James and I between us have taken it on as and when needed, and I intend to look at MQTT V5 updates soon. If anyone is interested in helping out, please let us know.

MQTT-SN

This client has taken a bit of a back burner for a while, partly because we have a creator and maintainer for the MQTT-SN transparent gateway in the shape of Tomoaki, who I had the pleasure of meeting recently in Singapore. For those that don’t know, MQTT-SN is a variant of MQTT explicitly designed for non-TCP networks such as UDP, ZigBee or BLE.

As it has not been standardized as MQTT has, it has been left behind a little. I hope that we can take steps to remedy that next year by looking at MQTT-SN within the OASIS MQTT TC. How exactly that will work hasn’t been formulated yet. I’ll keep everyone in touch as it happens. I hope Tomoaki and I can work together on some presentations about MQTT-SN for Eclipse IoT events next year.

Author: Ian Craggs

I work for IBM on the Watson IoT Platform. I am the project lead of Eclipse Paho, a member of the Eclipse IoT working group and Eclipse IoT PMC, and secretary of the OASIS MQTT standardization Technical Committee.

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