[zeromq-dev] NetMQ: Poller usage

[Doron Somech]

Hi Giacomo,

The poller is actually a copy of the zloop from czmq, actually I'm not big
fun of the event pattern but I want to make it as close as possible to
CLRZMQ.

1. The start method is blocking, you should call if from a dedicated thread.
2. Stop(false) just signal the dedicated thread to stop but don't actually
wait the thread is stopped, this is good when you want to close the poller
but continue doing something else with your code, but if for example you
closing the application and want to wait until the poller is completely
stopped call it with true.
3. Actually you cannot call Stop(true) from the dedicated thread, you can
call Stop(false) from the dedicated thread, but I don't have to implement
this kind of socket, you can just call Stop
4. Just call the stop method

Regarding the bonus question, you have to do some synchronization magic to
make it work, for the example let's call the socket which bind server and
the sockets which connect clients. So when the server binds no client is
connected yet (with inproc you have to bind before you can connect), now if
you will start send messages now the client will miss them.

After the client connected the client should send a signal message to the
server, after the server bind we wait for message from client, after this
the server can start publish messages.

If we are talking about pub-sub pattern you should have a sub socket as the
client, xpub socket as server, now the client immediately send subscribe
message and the server wait for the first message...

  Doron


On Fri, Jun 28, 2013 at 3:23 AM, Giacomo Tesio <giacomo at tesio.it> wrote:

> Hi, I'm having an hard time understanding the NetMQ.Poller usage (here:
> https://github.com/zeromq/netmq/blob/master/src/NetMQ/Poller.cs).
>
> The fact is, it doesn't expose any Poll method.
>
> I guess that this is done in the aim of OOP desing.
>
> But I'm not sure about its correct usage.
>
> My insight is that after adding the sockets to the Poller, I should simply
> observe the sockets' events ReceiveReady and SendReady, but if so:
>
>
>    1. does the Start method block? If not, this should mean that I don't
>    have to use it in a dedicated thread, right?
>    2. what are the pro/cons of Stop(false)?
>    3. one of the socket I added to the poller is a "control" one that
>    send a "STOP" command when required. In the event handler can I stop the
>    poller and remove the sockets?
>    4. what should I do to cleanup things (before context disposition)?
>
> Moreover I'd like to know if the socket events will ever be fired from
> sockets that aren't in a Poller, or not.
>
>
> Finally a bonus question (be patient, I'm a newbie here): I've read that
> with ZeroMQ I can loose a few messages at connection startup (even if I
> start the receiver before the sender): does this apply to inproc sockets
> too?
>
>
> Thanks a lot.
>
>
> Giacomo
>
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