mosquitto-users team mailing list archive

[Rene Kogels <renekogels@xxxxxxxxx>]

Hi Karl,

I did some more tests, and you are right, it takes 16 minutes before the
client discovers it lost the connection with eh broker and disconnects.

This is what I see on the client when I use netstat -an:
[
Active Internet connections (servers and established)
     Proto Recv-Q Send-Q Local Address           Foreign Address
State
     tcp        0      0 0.0.0.0:22              0.0.0.0:*
LISTEN
     tcp        0      0 192.168.5.3:22          192.168.5.50:65489
 ESTABLISHED
--->tcp        0  13061 192.168.5.3:33225       192.168.5.5:1883
 ESTABLISHED

I send subscribe messages every 10 secs, the Send-Q is getting bigger as
nothing gets acknowledged by the broker.

After 16 minutes I see this:
netstat -an
Active Internet connections (servers and established)
     Proto Recv-Q Send-Q Local Address           Foreign Address
State
     tcp        0      0 0.0.0.0:22              0.0.0.0:*
LISTEN
 -->tcp        0      1 192.168.5.3:33226       192.168.5.5:1883
 SYN_SENT

Connection gets a reset, and then the loop() becomes something else than 0
and escapes.

The settings on my Linux client determine how long it takes before a
connection is considered lost. It looks I might have to tweak these
settings a bit
to detect a lost connection sooner.

Thanks,
Rene


On Fri, Dec 13, 2013 at 5:51 PM, Karl Palsson <karlp@xxxxxxxxxxxx> wrote:

>
> How long are you waiting before deciding that it doesn't work?  You might
> have to wait for a
> TCP connection to timeout before the loop will fail, depending on your OS
> and network stack.
>
> There've been a couple of changes (long ago) that helped propagate this
> up, but pulling the
> plug on an intermediate cable, so no link detection triggers socket
> cleanup or anything can
> really take a while.
>
> Cheers,
> Karl P
>
>
> On Fri, Dec 13, 2013 at 04:49:48PM +0100, Rene Kogels wrote:
> > Thanks Nick. But still, loop() will not detect this. At least not with my
> > code, it will stay in the mosq_client.loop==0 loop when the connection to
> > the broker is lost. When I shut down the broker normally (service
> mosquitto
> > stop) the loop is stopped, and it tries to reconnect.
> >
> > Code (part):
> >
> > #Setup mosquitto client config
> > mosq_client = mosquitto.Mosquitto("client1")
> >
> > #Connect mosquitto client; if we cannot connect, we will notice later
> with
> > mosq_client.loop!=0
> > mosq_client.connect("some host")
> >
> > #Endless loop
> > while 1:
> >
> >   while mosq_client.loop()==0:
> >       #Put some code here to read serial port to get some data
> >
> >       #Publish it to the broker
> >       mosq_client.publish("serial/data", serial_data)
> >
> >   #If we are here, we lost the connection with the mosquitto broker, so
> > sleep first and then try to reconnect.
> >   print("No connection with broker. Sleeping before retrying...")
> >   time.sleep(10)
> >
> >   print("Trying to reconnect")
> >   mosq_client.connect("somehost")
> >
> >
> > Rene
> >
> >
> > On Fri, Dec 13, 2013 at 4:17 PM, Nicholas O'Leary  wrote:
> >
> > > Hi Rene,
> > >
> > > if the broker goes away, the tcp layer will notify the client side that
> > > the connection has been lost and the usual connection-lost processing
> will
> > > occur within the client.
> > >
> > > Regards,
> > > Nick
> > >
> > >
> > > On 12 December 2013 20:09, Rene Kogels  wrote:
> > >
> > >> Hi all,
> > >>
> > >> I have a question about the behaviour of a python program that
> publishes
> > >> data, but to a broker that lost its network connection after a while.
> The
> > >> loop() function will probably not detect this as it will only detect
> > >> changes on the network socket caused by the broker. In this case the
> broker
> > >> could not tell the publisher it lost the connection.
> > >>
> > >> Will the publisher keep sending data, assuming there is a broker? Or
> will
> > >> it detect somehow the broker is gone (TCP does not get an ack)? Will
> the
> > >> publish function block?
> > >>
> > >> Thanks,
> > >> Rene
> > >>
> > >>
> > >>
> > >> --
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> > >>
> > >>
> > >
>
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>