[zeromq-dev] Empty message does not close ZMQ_STREAM socket?

[KIU Shueng Chuan]

There's something in the manpage that your code doesn't do.

> To open a connection to a server, use the zmq_connect call, and then
fetch the socket identity using the ZMQ_IDENTITY zmq_getsockopt call.

I don't recall if this was strictly necessary but I see in my code that I
did fetch the identity but immediately discarded it.

I have some python scripts here where the server code disconnects the
client.
https://github.com/pijyoi/test_zmqstream
See zmqstream_publisher.py and zmqstream_subscriber.py

On 21 Mar 2016 5:07 pm, "Auer, Jens" <jens.auer at cgi.com> wrote:

> Hi,
>
> I am trying to close a TCP socket over a ZMQ_STREAM by sending an identity
> frame followed by an empty message, as described in the manual ("To close a
> specific connection, send the identity frame followed by a zero-length
> message"). I have a simple client/server example:
> #include <zmq.hpp>
> #include <iostream>
> #include <cstdlib>
>
> int main2() {
>     std::string address = "tcp://127.0.0.1:5000";
>
>     zmq::context_t zmq;
>     zmq::socket_t server(zmq, ZMQ_STREAM);
>
>     server.bind(address);
>
>     zmq::message_t id;
>     zmq::message_t m;
>     server.recv(&id);
>     server.recv(&m);
>     std::cout << "Connection received: " << id.size() << std::endl;
>
>     zmq::message_t empty{};
>
>     server.send(id, ZMQ_SNDMORE);
>     server.send(empty, ZMQ_SNDMORE );
>
>     int i;
>     std::cin >> i;
>
>     return 0;
> }
>
> #include <zmq.hpp>
> #include <iostream>
>
> int main() {
>     std::string address = "tcp://127.0.0.1:5000";
>
>     zmq::context_t zmq;
>     zmq::socket_t client(zmq, ZMQ_STREAM);
>
>     client.connect(address);
>
>     zmq::message_t m3;
>     zmq::message_t m4;
>     client.recv(&m3);
>     client.recv(&m4);
>
>     std::cout << "Connection established" << std::endl;
>
>     {
>         zmq::message_t m5;
>         zmq::message_t m6;
>         client.recv(&m5);
>         client.recv(&m6);
>     }
>
>     std::cout << "Connection closed" << std::endl;
>     int i;
>     std::cin >> i;
>
>     return 0;
> }
>
> When I start the server and then the client, the server will receive the
> connection message, but the empty message does not close the socket:
> ./stream_s 2
> Connection received: 5
> /tmp/stream_c
> Connection established
>
> tcp        0      0 127.0.0.1:5000          0.0.0.0:*
> LISTEN      32615/./stream_s
> tcp        0      0 127.0.0.1:5000          127.0.0.1:34270
> ESTABLISHED 32615/./stream_s
> tcp        0      0 127.0.0.1:34270         127.0.0.1:5000
> ESTABLISHED 32618/stream_c
>
> I have also created a second example where the server sends the close
> message twice. Here, the client actually receives the close message as an
> empty message. Why is this even possible over a ZMQ_STREAM socket?
>
> I am using ZeroMQ 4.1.4, so the notification messages should be enabled by
> default without setting ZMQ_STREAM_NOTIFY, and I have also tested 4.1.2 to
> check for a regression.
>
> Best wishes,
>   Jens
>
> _______________________________________________
> zeromq-dev mailing list
> zeromq-dev at lists.zeromq.org
> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.zeromq.org/pipermail/zeromq-dev/attachments/20160321/1ddc2ff8/attachment.htm>