[zeromq-dev] What exact networking problems ZMQ does solve?

[Randall Nortman]

On Thu, Dec 12, 2013 at 06:46:12PM +0200, artemv zmq wrote:
[...]
>    Now my question is going more to networking field. I want that kind of
>    situations when I can lose connection __but__ nor FIN, neither RST will be
>    generated . In other words I want to lose connection veyr silently (from
>    client perspective). Will be much appreciated for all that possible
>    scenarios. �Thanks in advance.

The situations are numerous -- anything happening to any piece of the
chain in between one application-level socket and the other can cause
this.  You have seen that at the host level a software firewall like
iptables can do it.  Here's a short, incomplete list of other
possibilities:

- Network cable unplugged on either end, or at any switch/router in
  between

- Power cable unplugged on either end, or at any switch/router

- Hardware or OS failure on either end, or at any switch/router

- Overloaded/malfunctioning network hop or component dropping packets

- Hackers (DDOS or other mayhem)

- Fiber-seeking backhoe

- Solar flares

- Alien invasion / zombie apocalypse

... etc. etc. etc.

The good news is that as an application developer, the solution to all
of these eventualities and more is the solution that's already been
mentioned: heartbeats to verify liveness, and/or request/response
architecture to verify receipt.  (These can be used individually or
combined; they give you different information.)