[zeromq-dev] ZeroMQ 2.1.11 - poll returns errno 11 on ZMQ_SUB sockets

[Rajalakshmi Iyer]

Hello,

I am trying a simple PUBLISH/SUBSCRIBE setup with ZeroMQ 2.1.11.

Here is the server code:

------------------------------------------------------------------------------------------------------------------------
#include <zmq.hpp>
#include <iostream>
using namespace std;

int main(void)
{
    try
    {
        zmq::context_t context(1);
        zmq::socket_t publisher(context, ZMQ_PUB);
        publisher.bind("tcp://*:5556");
        sleep(5);

        while(1)
        {
            char* command = "Command";
            zmq::message_t msg(command, strlen(command), NULL, NULL);
            if (!publisher.send(msg))
            {
                cout << "Unable to send message" << endl;
            }
            sleep(2);
        }
    }
    catch (zmq::error_t& e)
    {
        cout << "ZMQ Exception : " << e.what() << endl;
    }
    return 0;
}
------------------------------------------------------------------------------------------------------------------------

And this is the client code:
------------------------------------------------------------------------------------------------------------------------
#include <zmq.hpp>
#include <iostream>
using namespace std;

int main()
{
    try
    {
        zmq::context_t context(1);
        cout << "Serving commands ..." << endl;

        zmq::socket_t subscriber(context, ZMQ_SUB);
        subscriber.connect("tcp://localhost:5556");

        sleep(2);

        while(1)
        {
            zmq::pollitem_t items[] = {
                {(void*)subscriber, 0, ZMQ_POLLIN, 0}
            };

            int rc = zmq::poll(items, 1, 1);
            cout << "zmq_poll(rc=" << errno << ")" << endl;

            if (items[0].revents & ZMQ_POLLIN)
            {
                zmq::message_t command;
                if (!subscriber.recv(&command, ZMQ_NOBLOCK))
                {
                    cout << "Failed to receive command" << endl;
                }
                cout << "Received command: " << (char*)command.data() <<
endl;
            }
        }
    }
    catch (zmq::error_t& e)
    {
        cout << "ZMQ Exception : " << e.what() << endl;
    }
    return 0;
}
------------------------------------------------------------------------------------------------------------------------


The server is sending commands every 2 seconds over the ZMQ_PUB socket. The
client does zmq_poll on the ZMQ_SUB socket in a loop. However, the client
always sees errno 11 on a zmq_poll (which seems to indicate Resource
Temporarily Unavailable).

I have tried to figure out the cause from other posts in the mailing lists.
They seemed to indicate adding a sleep after the bind/connect phase before
starting to send/recv data. Even that has not helped.

Apologies, if this has been answered earlier, but it would be really great
if someone can help me out here.

Thanks,
Raj.

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