[zeromq-dev] http://hintjens.com/blog:85#toc5

[Luca Boccassi]

On Sun, 2017-05-14 at 09:08 -0400, Kevin Meredith wrote:
> Hi -
> 
> Reading Pieter's above listed blog post, he noted:
> 
> > we introduced the rule that new stable releases of the software
> > must (a)
> 
> talk to old stable releases and (b) they must support existing apps,
> without changes. We more or less succeeded with that, so ZeroMQ
> versions
> 3.2 and 4.0 work nicely with 2.2 and 2.1, for example.
> 
> I am interested to learn what this means.
> 
> Does the above example mean that a 3.2 PUB could talk to a 2.2 SUB,
> for
> example?
> 
> Thank you,
> Kevin

With regards to the network protocol (ZMTP), yes, libzmq supports all
versions of the protocol, it detects it at runtime and uses the
relevant encoder/decoder to talk with the peer(s).
There were a couple of bugs that prevented full compatibility but they
have been fixed last year. We do lack automated cross-compatibility CI
tests though, there's an item on the issue tracker for it - help from
volunteers would be very welcome.

Regarding the library itself, API compatibility was broken with 3.0,
and maintained since then.

ABI compatibility was last broken with 4.1.0.

Kind regards,
Luca Boccassi
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