Can't switch between pair version 0 and 1

[JenWa]

Hello,

first of all thank you for this project!

I have two projects which use nanomsg for ipc communication (one in Go and the other in Typescript) and now I want to have a third project in C# which uses NNG (this project) to communicate with the other ones.
The Req/Rep pattern works perfectly. I have some difficulties with the Pair pattern:

When I communicate with pair sockets created by NNG everything is fine. Same for pair sockets created by nanomsg.
But if one pair socket is created by nanomsg, and I try to listen or send messages to the pair socket created by NNG (and vice versa), it doesn't work.

I found out that NNG supports a pair version 1 protocol, which nanomsg doesn't (mangos v2) and looking at your code, it seems like the issue could be that you just expose creating pair sockets with version 1 protocol ?

<Factory.cs>
public NngResult<IPairSocket> PairOpen() => Pair1Socket.Open();

I didn't find a way to call Pair0Socket.Open();

It would be awesome to also have the option to create pair sockets which use the version 0 protocol so that the interoperability between NNG and nanomsg is granted.

Thank you for any reply in advance!

[jeikabu]

Yeah, we definitely want pair 0 support.

The intention was to create different factories that expose the various versions of the sockets similar to what's done in our Rust wrapper. Basically, create another implementation of IAPIFactory where PairOpen() returns a pair0 instead of pair1.

I'll accept the (much appreciated) PR and create an issue to flesh it out later.