[zeromq-dev] PUB sent, but SUB can not receive.

[Richard_Newton at waters.com]

Is this on windows?

If so the stl implementation on widows (and clangs implementation, but not gcc) uses something called the small string optimisation, any string less
than or equal to 16 characters will be stored within the string class itself so will copy over, anything more than 16 characters will be allocated on
the heap and string will keep a pointer to it, this will not be copied over.

So try a symbol with more than 16 characters and it will probably fail.

Ric.




From:	liuchuanbo at gmail.com
To:	"ZeroMQ development list" <zeromq-dev at lists.zeromq.org>,
Cc:	zeromq-dev-bounces at lists.zeromq.org
Date:	14/08/2013 01:59 PM
Subject:	Re: [zeromq-dev] PUB sent, but SUB can not receive.
Sent by:	zeromq-dev-bounces at lists.zeromq.org



Hi, Ric

Right, string is std::string.
Why Symbol(also std::string) has the correct string and Time NOT?

I'm debugging now, WData.Time is ""(a empty string).

On Aug 14, 2013, at 8:54 PM, Richard_Newton at waters.com wrote:



      Is string here a std::string?  If so you cannot do this as std::string uses more memory internally,

      You'll need either a struct that uses just data arrays like:


      typedef struct tag_WData
      {
      charTime[100];
      char Symbol[100];
      } WData;

      Or use some serialisation mechanism such as protocol buffers.

      Ric.



      <graycol.gif>liuchuanbo---14/08/2013 01:45:26 PM---Hi, everyone My problem is as the following:

      From: liuchuanbo at gmail.com
      To: zeromq-dev at lists.zeromq.org,
      Date: 14/08/2013 01:45 PM
      Subject: [zeromq-dev] PUB sent, but SUB can not receive.
      Sent by: zeromq-dev-bounces at lists.zeromq.org





      Hi, everyone
      My problem is as the following:

      typedef struct tag_WData
      {
      string Time;
      string Symbol;
      } WData;


      On the PUB side. I can get WData.Time.

      void OnData(WData wd)
      {
      // PUB Socket send ticker message to subscriber
      int msgSize = sizeof(WData);
      zmq::message_t message(msgSize);
      memcpy ((void *) message.data(), &wd, msgSize);

      publisher.send(message);
      }


      However, on the SUB side, it's very wired that I can NOT get WData.Time, but WData.Symbol is correct.

      int main (int argc, char *argv[])
      {
      zmq::context_t context (1); // only 1 io_threads
      zmq::socket_t subscriber (context, ZMQ_SUB);
      subscriber.connect("tcp://localhost:5556");

      subscriber.setsockopt(ZMQ_SUBSCRIBE, NULL, 0);

      WData *msg;
      while(true){
      zmq::message_t message(sizeof(WData));
      subscriber.recv(&message);
      msg = (WData *) message.data();

      // it's ERROR here. error message: Bad ptr
      cout << msg->Time << endl;
      }

      return 0;
      }

      Why?
      Thanks!

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