[zeromq-dev] Is UDP transport needed in ZeroMQ?

Bruno D. Rodrigues bruno.rodrigues at litux.org
Sat Dec 28 20:05:48 CET 2013

On Dec 28, 2013, at 17:26, Michael Powell <mwpowellhtx at gmail.com> wrote:

> On Sat, Dec 28, 2013 at 11:05 AM, Daniel Krikun <dkrikun0 at gmail.com> wrote:
>> What I wanted to say is that while patterns do simplify development, they
>> have there peculiarities, in the example above, i'm doing non-blocking
>> receive with REQ/REP which looks benign, but in fact it isn't because if the
>> message is not obtained, i cannot send().
> I don't know your code, but it sounds like a bug worst case, possibly
> a feature request best case. You would likely need to report it,
> probably clarify what you mean by "if the 'message' is not obtained",
> what it is you mean by "I cannot send".

This is a quite clear case and well documented on the book and patterns. Peer A sends a message. Something wrong happens with peer B that doesn’t receive the message, or doesn’t reply, or replies but the message never gets back to A. Peer A is dead locked. Peer A needs to disconnect and reconnect. Now if peer A was for whatever reason doing a bind, it would need to fully kill the socket and create a new one.

I think simple answer is to never use REP/REQ but instead use DEALER/ROUTER combinations ;) (/me ducks)

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