3 files changed, 16 insertions, 3 deletions
diff --git a/src/zmq_engine.cpp b/src/zmq_engine.cpp
index 3e98c53..815697c 100644
--- a/src/zmq_engine.cpp
+++ b/src/zmq_engine.cpp
@@ -40,7 +40,8 @@ zmq::zmq_engine_t::zmq_engine_t (fd_t fd_, const options_t &options_) :
     outsize (0),
     encoder (out_batch_size),
     inout (NULL),
-    options (options_)
+    options (options_),
+    plugged (false)
 {
     //  Initialise the underlying socket.
     int rc = tcp_socket.open (fd_, options.sndbuf, options.rcvbuf);
@@ -49,10 +50,14 @@ zmq::zmq_engine_t::zmq_engine_t (fd_t fd_, const options_t &options_) :
 
 zmq::zmq_engine_t::~zmq_engine_t ()
 {
+    zmq_assert (!plugged);
 }
 
 void zmq::zmq_engine_t::plug (io_thread_t *io_thread_, i_inout *inout_)
 {
+    zmq_assert (!plugged);
+    plugged = true;
+
     //  Conncet to session/init object.
     zmq_assert (!inout);
     zmq_assert (inout_);
@@ -72,6 +77,9 @@ void zmq::zmq_engine_t::plug (io_thread_t *io_thread_, i_inout *inout_)
 
 void zmq::zmq_engine_t::unplug ()
 {
+    zmq_assert (plugged);
+    plugged = false;
+
     //  Cancel all fd subscriptions.
     rm_fd (handle);
 
diff --git a/src/zmq_engine.hpp b/src/zmq_engine.hpp
index bdd2a5d..363eaaf 100644
--- a/src/zmq_engine.hpp
+++ b/src/zmq_engine.hpp
@@ -39,7 +39,6 @@ namespace zmq
     public:
 
         zmq_engine_t (fd_t fd_, const options_t &options_);
-        ~zmq_engine_t ();
 
         //  i_engine interface implementation.
         void plug (class io_thread_t *io_thread_, struct i_inout *inout_);
@@ -54,6 +53,10 @@ namespace zmq
 
     private:
 
+        //  Destructor is not to be used directly.
+        //  Use 'terminate' function instead.
+        ~zmq_engine_t ();
+
         //  Function to handle network disconnections.
         void error ();
 
@@ -72,6 +75,8 @@ namespace zmq
 
         options_t options;
 
+        bool plugged;
+
         zmq_engine_t (const zmq_engine_t&);
         void operator = (const zmq_engine_t&);
     };
diff --git a/src/zmq_init.cpp b/src/zmq_init.cpp
index ee5741a..ba9706c 100644
--- a/src/zmq_init.cpp
+++ b/src/zmq_init.cpp
@@ -49,7 +49,7 @@ zmq::zmq_init_t::zmq_init_t (io_thread_t *io_thread_,
 zmq::zmq_init_t::~zmq_init_t ()
 {
     if (engine)
-        delete engine;
+        engine->terminate ();
 }
 
 bool zmq::zmq_init_t::read (::zmq_msg_t *msg_)