Problem: ZMQ_STREAM cannot disconnect when SNDHWM is reached

Solution: defer HWM check to the second frame in stream_t::xsend

Author: guyco3

src/stream.cpp

@@ -79,9 +79,6 @@ int zmq::stream_t::xsend (msg_t *msg_)
                 _current_out = out_pipe->pipe;
                 if (!_current_out->check_write ()) {
                     out_pipe->active = false;
-                    _current_out = NULL;
-                    errno = EAGAIN;
-                    return -1;
                 }
             } else {
                 errno = EHOSTUNREACH;
@@ -119,6 +116,11 @@ int zmq::stream_t::xsend (msg_t *msg_)
             _current_out = NULL;
             return 0;
         }
+        if (!_current_out->check_write()) {
+            _more_out = true;
+            errno = EAGAIN;
+            return -1;
+        }
         const bool ok = _current_out->write (msg_);
         if (likely (ok))
             _current_out->flush ();