On Thu, May 31, 2012 at 3:21 PM, Marco Trapanese <marcotrapanese at gmail.com> wrote: > printf("errno = %d\n", zmq_errno()); > int rc = zmq_setsockopt (publisher, ZMQ_HWM, &hwm, sizeof (hwm)); > printf("errno = %d\n", zmq_errno()); The fact that errno changes is not significant. If rc is 0, errno is _not_ significant. -Pieter