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Re: [mosquitto-dev] Bridging on a wakeup or connection

I also had a need to send commands to Mosquitto.  I implemented a mechanism for a client connected as an authorized user to send commands using normal MQTT publish to a special topic.  The mechanism is rudimentary in that there is no output to the client in response to the command, but it works for my situation.

-----Original Message-----
From: mosquitto-dev-bounces@xxxxxxxxxxx [mailto:mosquitto-dev-bounces@xxxxxxxxxxx] On Behalf Of Ian Craggs
Sent: Wednesday, July 23, 2014 5:41 AM
To: mosquitto-dev@xxxxxxxxxxx
Subject: Re: [mosquitto-dev] Bridging on a wakeup or connection

#1 In RSMB, I have the capability to stop and restart bridges with a command (read from a file).  And create new ones.  I think it would be good to add that to Mosquitto, but Roger was wondering how to best accept commands in Mosquitto, last time we discussed the topic.

#2 that could be done via MQTT?  Mosquitto could send some information about the bridge starting (I think there might be a state change already indicated).  Of course there would have to be an MQTT client running to listen for the signal and start the modem call.


On 07/22/2014 07:31 AM, Frank Pagliughi wrote:
> Hi,
> I'm testing out using Mosquitto on an embedded ARM board as a means of 
> sending messages between the on-board apps. Everything is good there.
> Now I'm starting to play with bridging the broker to remote servers to 
> get data off the board. When awake and connected to a LAN, it's 
> working fine, but there are two situations with a similar pattern that 
> I need help with:
> (1) The board is asleep most of the time, and the Ethernet controller 
> powers down in suspend mode, severing TCP connections to the LAN. The 
> board only remains awake for 5-10sec at a time. So immediately upon 
> resume, it would be great to kick the broker to tell it to reconnect 
> the bridge(s) and start pumping out the messages.
> (2) The machine may be deployed in a remote location with a 
> cell/satellite modem in which case it has no LAN. It still wakes every 
> few minutes, but only once every few hours does it power up the modem 
> and make a short phone call to upload data.
> In the first case it may suffice to use automatic "start_time" and use 
> a very small "restart_timeout" - like 1. The broker wouldn't
> (couldn't) thrash through the suspend, and would reestablish the 
> connection very quickly on wakeup. I assume.
> But in the second case, it would be better for the broker to not be 
> re-trying constantly, using CPU and battery time. What could I do 
> here? Is there an existing configuration that might work?
> But into the future...
> Wish #1:  It would be cool in either case to be able to give the 
> broker a kick to say, "try to reconnect your bridges now". Obviously a 
> signal would do the trick. It could be sent from a ppp-up or resume 
> script.
> Wish #2: In the second (modem) case, the other way around might be a 
> way to go. Rather then the system telling mosquitto when it's time to 
> reconnect, mosquitto could tell the board when it's time to place a 
> call. Use "lazy" startup with a threshold count, and have the broker 
> emit a signal of some sort (maybe run a script or system command) when 
> it's time to make a connection. Allow the system to make the call.
> Emit another signal when the idle_timeout expired (hang up the phone).
> Thanks,
> Frank
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Ian Craggs
icraggs@xxxxxxxxxx                 IBM United Kingdom
Committer on Paho, Mosquitto

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