[zeromq-dev] Q: socket type/pattern for protocol exchange

[Michael Haberler]

Am 10.06.2013 um 11:05 schrieb Pieter Hintjens <ph at imatix.com>:

> On Mon, Jun 10, 2013 at 9:33 AM, Michael Haberler <mail17 at mah.priv.at> wrote:
> 
>> I am about to implement a protocol between peers; the phases and interactions being roughly:
>> 
>> - an negotiation phase (peers exchange options and reach agreement or dont)
>> - an 'open' phase entered on agreement, where state updates flow either direction as needed, not necessarily requiring confirmation
>> - a shutdown phase initiated by either side
>> 
>> Potentially there might be more than two peers. Message flows and encoding are done (protobuf).
> 
> It's a fairly common use case and I'd tend to recommend an asymmetric
> protocol with ROUTER at the "server" and DEALER at the "client"; there
> are examples of this in the Guide, especially Chapter 7. If you want a
> symmetric network you can try the Harmony pattern from Chapter 8.

I need another smack on the head,)

ROUTE/DEALER worked fine (I dont need symmetric) for a single thread

extending to multiple clients I'd think one worker thread per client seems the way to go, since that worker thread will also be the natural place to manage per-client  protocol state

That would suggest a binding of worker thread to a client at initial exchange based on client socket identity, not distribution based on load

the first step could look like so:

- once a client identity is seen first time, start a worker thread and create an associated per-worker inproc socket (?)

The remaining plumbing is unclear to me:
- the main thread could push messages based on identity down that per-worker socket, and pull replies back from same (then probably REQ/REP would be the right mode)
- a worker could subscribe to a certain identity and either reply directly (?) or by passing a reply back to the DEALER (?) 
- I'm unclear if a device is appropriate here

grateful for a suggestion,

Michael