[zeromq-dev] Sub problem

Pieter Hintjens ph at imatix.com
Fri Dec 14 00:20:09 CET 2012

Hi Stefan,

Are you connecting SUB to PUB via some firewall or proxy, or is this a
direct connection?

Also, is the publisher silent for long periods of time?

The reason I ask is that we've seen connections going 'stale'
sometimes; TCP not reporting an error at the client side but not
transmitting anything. It's due to some proxy in the middle getting
confused, presumably.

If this is happening, consider sending keep-alive messages from PUB to
SUB, which the SUB can discard (but must subscribe to, in 3.2).


On Thu, Dec 13, 2012 at 11:19 PM, Stefan de Konink <stefan at konink.de> wrote:
> Hi,
> I am still observing a case were a connected ZeroMQ Sub is still not
> receiving any data anymore after a certain period of idle time without
> any data. We are willing to test this with exact numbers (our estimation
> is that less than 4 hours no data results in a dead client) but in the
> mean time I was reasoning about problem.
> My hypothesis of this 'dead client' is that the socket is for some
> reason in a disconnected state, after it reconnects it does not apply
> the 'original' socket options. This cannot be reproduced using normal
> code, a socket in ZeroMQ can't be closed and then reconnected or rebinded.
> Obviously we are going to see if we can reproduce the problem, and
> tcpdumping the connection to find out if the client is really receiving
> new data, or that the client is truly 'disconnected'.
> Would anyone be willing to take a peak if there is any basis for this
> reasoning?
> Stefan
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