clients can now intercept the heartbeat negotiation, and install a shorter of longer heartbeat interval, and clients can be notified for received heartbeat frames

include/connectionhandler.h

@@ -25,6 +25,27 @@ namespace AMQP {
 class ConnectionHandler
 {
 public:
+    /**
+     *  Method that is called when the heartbeat frequency is negotiated
+     *  between the server and the client. You normally do not have to
+     *  override this method, because in the default implementation the
+     *  suggested heartbeat is simply accepted by the client.
+     *
+     *  However, if you want to disable heartbeats, or when you want an
+     *  alternative heartbeat interval, you can override this method
+     *  to use an other interval. You should return 0 if you want to
+     *  disable heartbeats.
+     *
+     *  @param  connection      The connection that suggested a heartbeat interval
+     *  @param  interval        The suggested interval from the server
+     *  @return uint16_t        The interval to use
+     */
+    virtual uint16_t onNegotiate(Connection *connection, uint16_t interval)
+    {
+        // default implementation, suggested heartbeat is ok
+        return interval;
+    }
+
     /**
      *  Method that is called when data needs to be sent over the network
      *
@@ -38,6 +59,17 @@ public:
      */
     virtual void onData(Connection *connection, const char *buffer, size_t size) = 0;
 
+    /**
+     *  Method that is called when the server sends a heartbeat to the client
+     *
+     *  You do not have to do anything here, the client sends back a heartbeat
+     *  frame automatically, but if you like, you can implement/override this
+     *  method if you want to be notified of such heartbeats
+     *
+     *  @param  connection      The connection over which the heartbeat was received
+     */
+    virtual void onHeartbeat(Connection *connection) {}
+
     /**
      *  When the connection ends up in an error state this method is called.
      *  This happens when data comes in that does not match the AMQP protocol

include/connectionimpl.h

@@ -368,10 +368,22 @@ public:
 
     /**
      *  Set the heartbeat delay
-    */
-    void setHeartbeat(uint16_t heartbeat)
+     *  @param  heartbeat       suggested heartbeat by server
+     *  @return uint16_t        accepted heartbeat by client
+     */
+    uint16_t setHeartbeat(uint16_t heartbeat)
     {
-        _heartbeat = heartbeat;
+        // pass to the handler
+        return _heartbeat = _handler->onNegotiate(_parent, heartbeat);
+    }
+
+    /**
+     *  Report a heartbeat to the connection handler
+     */
+    void reportHeartbeat()
+    {
+        // pass to handler
+        _handler->onHeartbeat(_parent);
     }
 
     /**

include/tcpconnection.h

@@ -42,6 +42,13 @@ private:
      */
     Connection _connection;
     
+    /**
+     *  Method that is called when the heartbeat frequency is negotiated.
+     *  @param  connection      The connection that suggested a heartbeat interval
+     *  @param  interval        The suggested interval from the server
+     *  @return uint16_t        The interval to use
+     */
+    virtual uint16_t onNegotiate(Connection *connection, uint16_t interval) override;
 
     /**
      *  Method that is called by the connection when data needs to be sent over the network
@@ -51,6 +58,12 @@ private:
      */
     virtual void onData(Connection *connection, const char *buffer, size_t size) override;
 
+    /**
+     *  Method that is called when the server sends a heartbeat to the client
+     *  @param  connection      The connection over which the heartbeat was received
+     */
+    virtual void onHeartbeat(Connection *connection) override;
+
     /**
      *  Method called when the connection ends up in an error state
      *  @param  connection      The connection that entered the error state

include/tcphandler.h

@@ -25,12 +25,35 @@ class TcpConnection;
 class TcpHandler
 {
 public:
+    /**
+     *  Method that is called when the heartbeat frequency is negotiated
+     *  between the server and the client. 
+     *  @param  connection      The connection that suggested a heartbeat interval
+     *  @param  interval        The suggested interval from the server
+     *  @return uint16_t        The interval to use
+     *
+     *  @see ConnectionHandler::onNegotiate
+     */
+    virtual uint16_t onNegotiate(TcpConnection *connection, uint16_t interval)
+    {
+        // default implementation, suggested heartbeat is ok
+        return interval;
+    }
+
     /**
      *  Method that is called when the TCP connection ends up in a connected state
      *  @param  connection  The TCP connection
      */
     virtual void onConnected(TcpConnection *connection) {}
 
+    /**
+     *  Method that is called when the server sends a heartbeat to the client
+     *  @param  connection      The connection over which the heartbeat was received
+     *
+     *  @see    ConnectionHandler::onHeartbeat
+     */
+    virtual void onHeartbeat(TcpConnection *connection) {}
+    
     /**
      *  Method that is called when the TCP connection ends up in an error state
      *  @param  connection  The TCP connection

src/connectiontuneframe.h

@@ -138,10 +138,10 @@ public:
         Monitor monitor(connection);
         
         // store the heartbeat the server wants 
-        connection->setHeartbeat(heartbeat());
+        uint16_t interval = connection->setHeartbeat(heartbeat());
 
         // send it back
-        connection->send(ConnectionTuneOKFrame(channelMax(), frameMax(), heartbeat()));
+        connection->send(ConnectionTuneOKFrame(channelMax(), frameMax(), interval));
         
         // check if the connection object still exists
         if (!monitor.valid()) return true;

src/heartbeatframe.h

@@ -57,6 +57,9 @@ public:
      */
     virtual bool process(ConnectionImpl *connection) override
     {
+        // notify the connection-handler
+        connection->reportHeartbeat();
+        
         // send back the same frame
         connection->send(*this);
 

src/tcpconnection.cpp

@@ -62,6 +62,18 @@ void TcpConnection::process(int fd, int flags)
     _state = result;
 }
 
+/**
+ *  Method that is called when the heartbeat frequency is negotiated.
+ *  @param  connection      The connection that suggested a heartbeat interval
+ *  @param  interval        The suggested interval from the server
+ *  @return uint16_t        The interval to use
+ */
+uint16_t TcpConnection::onNegotiate(Connection *connection, uint16_t interval)
+{
+    // the state object should do this
+    return _state->reportNegotiate(interval);
+}
+
 /**
  *  Method that is called by the connection when data needs to be sent over the network
  *  @param  connection      The connection that created this output
@@ -74,6 +86,16 @@ void TcpConnection::onData(Connection *connection, const char *buffer, size_t si
     _state->send(buffer, size);
 }
 
+/**
+ *  Method that is called when the server sends a heartbeat to the client
+ *  @param  connection      The connection over which the heartbeat was received
+ */
+void TcpConnection::onHeartbeat(Connection *connection)
+{
+    // let the state object do this
+    _state->reportHeartbeat();
+}
+
 /**
  *  Method called when the connection ends up in an error state
  *  @param  connection      The connection that entered the error state

src/tcpstate.h

@@ -79,6 +79,17 @@ public:
         // default does nothing
     }
 
+    /**
+     *  Report that heartbeat negotiation is going on
+     *  @param  heartbeat   suggested heartbeat
+     *  @return uint16_t    accepted heartbeat
+     */
+    uint16_t reportNegotiate(uint16_t heartbeat)
+    {
+        // pass to handler
+        return _handler->onNegotiate(_connection, heartbeat);
+    }
+    
     /**
      *  Report to the handler that the object is in an error state
      *  @param  error
@@ -89,6 +100,15 @@ public:
         _handler->onError(_connection, error);
     }
 
+    /**
+     *  Report that a heartbeat frame was received
+     */
+    void reportHeartbeat()
+    {
+        // pass to handler
+        _handler->onHeartbeat(_connection);
+    }
+    
     /**
      *  Report to the handler that the connection is ready for use
      */