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Re: [paho-dev] Problem with routing

Hi Antti,
Âtry to telnet the remote ip/port, just to understand if is a MQTT problem or network one...


Domenico



Il 05/04/2018 15:05, Antti GÃrding ha scritto:
Hi,

I am writing a Python 3.4 application that uses Paho as the MQTT client library. It has been working mostly fine, but I have now encountered a sudden problem and I wonder if someone on this list could assist me with it.

I am connecting to a server over ethernet and there is a company's firewall between my software and the server. It has worked fine for the 1,5 years I have been doing this development, except for two occasions, which seem similar to me. The first time the problem occured, the IT support was able to fix it in a day by doing something about NAT. Now the problem came back, and while it looks the same to me, the IT support hasn't been able to fix it again. There is a suspect that some router would have been replaced and that would have altered some settings, but that's just a guess.

What happens is that when I call Paho's connect(), trying to bind to a particular IP address (the device has several network interfaces), connect() just won't return. Ever.

When that happens and I attempt to make sure the ethernet connection works in general by pinging 8.8.8.8, I get this:
ping -I eth1 8.8.8.8
PING 8.8.8.8 (8.8.8.8) from 82.195.211.99 eth1: 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=52 time=22.5 ms
From 82.195.210.1: icmp_seq=1 Redirect Host(New nexthop: 82.195.210.2)
From 82.195.210.1: icmp_seq=2 Redirect Host(New nexthop: 82.195.210.2)
64 bytes from 8.8.8.8: icmp_seq=2 ttl=52 time=22.8 ms
From 82.195.210.1: icmp_seq=3 Redirect Host(New nexthop: 82.195.210.2)
64 bytes from 8.8.8.8: icmp_seq=3 ttl=52 time=25.4 ms

What catches my attention is this: "Redirect Host(New nexthop: 82.195.210.2)". When everything works fine, that won't appear. I'm just not enough a network guy to say anything more. I am just stating what I am seeing.

Just for the sake of comparison, this is what I get when I ping the same address via a mobile connection that Paho uses with no problem:
ping -I wwan0 8.8.8.8
PING 8.8.8.8 (8.8.8.8) from 100.88.155.57 wwan0: 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=55 time=883 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=55 time=357 ms

Does anyone have any idea of what might be going on? Is there something I can do to fix this in how I use Paho? Or is this something about Paho, and if it is, could it be something the community might want to fix?


Best Regards,
Antti GÃrding


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