Skip to main content

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [List Home]
Re: [paho-dev] Mqtt Paho - Trying to publish while broker is unreachable


my RSMB broker (for which the code is in the Mosquitto project) has dynamic bridges (and has had for several years). 

Your suggestion is interesting.  If we published to a broker topic (possibly prefixed by a $ as alternative behaviour is allowed in the 3.1.1 spec), then a normal MQTT application could listen for any such message, and set up a dynamic bridge to the remote system.  You can do this with RSMB today (except that RSMB does not persist messages to disk so messages are lost over a restart).

Dynamic bridges is a feature I was thinking of asking if Roger wanted to add to Mosquitto.

This is an option I had previously thought of rather than implementing offline buffering in the clients.  But given that very simple offline buffering should be easy to add, both approaches could have their place.   Do you agree?


On 22/01/14 12:50, Paul Fremantle wrote:

That brings up an interesting question: If I do the model you suggest, then the local mosquitto broker must have a hard-coded definition of the remote broker. That is ok in many cases, but in general it might be nice to have a way of specifying the address of the broker in the topic name:

e.g. instead of just topicA/topicB, put mqtt:// at which point my local broker will know this needs to go to the broker

This then becomes a bit like SMTP, where I config my local mail client to talk to my well-known, trusted, available SMTP server, and it then does the onward forwarding of my mail to the correct SMTP server for the recipient. 


On 22 January 2014 09:32, Ian Craggs <icraggs@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hi Pablo,

the short answer is that you have to handle the situation by yourself.   Having some buffering capability in the client is something that you are not alone in asking for.  I'll make sure to add that to our requirements.

One way you can address this, is, as you point out, with a local Mosquitto broker and a bridge.


On 21/01/14 21:31, Pablo Lopez wrote:

Hi all paho-dev members.

This is my first (baby) step in the "Internet of things" world, and I'm having a hard time with it :)

Let me introduce myself : I'm Pablo, a french developer who is trying to connect raspberry pi sensors to a central server to process sensors values. 

But I'm having a hard time handling WiFi instability in my environment.

So I'm copying here a message I already put in the open on StackOverflow

Thank you for any help you could provide.

I'm going back to the Java Paho source code to try answering my question by myself ;)

I'm begininng to use Mqtt and I have a hard time with handling an unreliable network. I'm using a Paho Java Client (in groovy) to publish messages to a distant Mosquitto Broker.

Is there a way, when the broker is unreachable, to have the Paho client persist the message and automatically re-connect to the broker and publish the locally stored messages ? Do I have to handle everything myself, using for example a local broker ?

Here is my client building code

    String pe
Dir = config['persistence-dir'] ?: System.getProperty('')
    def persistence = new MqttDefaultFilePersistence(persistenceDir)
    client = new MqttClient(uri, clientId, persistence)
    options = new MqttConnectOptions()
    if (config.password) {
        options.setPassword(config.password as 

And my publish code

  def message = new MqttMessage(Json.encode(outgoingMessage).getBytes())
    try {
    def topic = client.getTopic('processMsg')
    def token = topic.publish(message)
    if (client) {


Pablo Lopez
email & gtalk : plopez@xxxxxxxx / mob: +33-
Xebia, Software Development Done Right.

paho-dev mailing list

paho-dev mailing list

Paul Fremantle
Part-time PhD student - School of Computing
twitter: pzfreo / skype: paulfremantle / blog:
CTO and Co-Founder, WSO2
OASIS WS-RX TC Co-chair, Apache Member
07740 199 729

paho-dev mailing list

Back to the top