Cannot get Arduino to connect to Raspberry Pi MQTT broker about pubsubclient

[knolleary]

The rc=-4 means the client connected, but the server didn't respond to the connect request (http://knolleary.github.io/pubsubclient/api.html#state). This usually indicates the broker you're running doesn't support the 3.1.1 version of MQTT so doesn't know how to respond.

You should either upgrade your broker (assuming its mosquitto, you need at least v1.3, although the latest available is 1.4.3.

Otherwise, change the MQTT_VERSION header in PubSubClient.h to switch the library to use MQTT 3.1.

[noemark1]

I tried changing the MQTT_VERSION header in PubSubClient.h to use MQTT 3.1 by commenting out the 3.1.1 line and removing the comment from 3.1. I restarted IDE and recompiled - same result. How do I find out what version of mosquitto I am running on the Pi? I installed it a few days ago using sudo apt-get install mosquitto mosquitto-clients python-mosquitto

Many thanks,

-Mark

[knolleary]

Running:
$ dpkg -l mosquitto

should tell you something.

I haven't got a Pi to hand at the moment to check, but I suspect the version in the repositories may be slightly out of date. Some good instructions for installing latest/greatest here: http://jpmens.net/2013/09/01/installing-mosquitto-on-a-raspberry-pi/

[noemark1]

It claims it is running v 0.15, which is 3.1 compatible. I am trying to download the newest version from the server at the link you provided me above, but the server is hanging. Will try again later.

While I have you here , what are the other likely reasons for the -4 error?

Thank you for your help, as I am a relatively inexperienced user of Linux and the Arduino platform.

Many thanks,

-Mark

[knolleary]

Hmm, not sure what package version 0.15 maps to in terms of actual mosquitto version. Have a look under /var/log/ for any mosquitto related log files - it logs its version number on start up.

This is the only concrete cause of the -4 result I know of. I suggest you try changing the MQTT_VERSION value in PubSubClient.h - if I'm right about this being a version mismatch issue, that'll get things working.

It is still worth trying to get the newer version of mosquitto on there; lots of good bug fixes etc.

[noemark1]

And you are right sir - I just upgraded to version 1.4.3 and everything connects fine. Thank you for your help. Now to get all of my wireless nodes working...

Many thanks,

-Mark