[zeromq-dev] Using zeromq in a distributed load pipeline, can I get the address of the last server a message was sent to?

John Connor john.theman.connor at gmail.com
Sat Oct 2 04:13:10 CEST 2010

Thanks for the reply Joshua,
But I still don't understand why the send function can't return the
address that it sent the message to "because it is async".  Why should
that have any effect on whether or not it exposes the address of the
endpoint it sent to?  Once connected, is the address no longer stored
in a usable form?
I don't want to have to use req/rep just so that the receiver can tell
the sender that it got the message and what its address is, that seems
like way over kill.  TCP ensures that the receiver will get the
message, and the sender already knows the address its sending to, so
the whole req/rep thing seems redundant.  Its looking like the only
solution is for me to maintain a list of separate sockets and iterate
over them when sending messages so that I know what server I'm sending
the message to.  Do you know if there would be a lot of overhead with
creating multiple sockets instead of multiple connections?
I appreciate your help,

On Fri, Oct 1, 2010 at 8:26 PM,  <zeromq-dev-request at lists.zeromq.org> wrote:
> No, ZeroMQ doesn't expose where it sends the data because it is asynchronous. If you need this information, you can possibly do it with a request/reply. The request being the msg sent to the server, the reply being the information from that specific server.
> You should also change from DOWNSTREAM/UPSTREAM to PUSH/PULL because the downstream/upstream naming is deprecated.
> Joshua
> On Oct 1, 2010, at 5:41 PM, John Connor wrote:
>> Hello,
>> Sorry if this question is a dupe, but I'm just starting to use zeromq
>> for a project, and I have looked everywhere for an answer to this
>> question:
>> If I set up a pipeline which distributes load across a cluster, I
>> would like to log on the sender where its messages get sent. This is
>> what I have in mind (python):
>> import zmq
>> context = zmq.Context()
>> socket = context.socket(zmq.DOWNSTREAM)
>> socket.connect("tcp://")
>> socket.connect("tcp://")
>> msg = "Hello World\0"
>> connection_string = socket.send(msg)
>> # should print "Sent message to tcp://"
>> print "Sent message to", connection_string
>> But I cant find anything that talks about this. Any help at all is appreciated.
>> Thanks,
>> --Connor
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