net: Fix some observed problems

It seems the client sends application messages before the session has been established.

src/protocol/net/DMLSession.cpp

@@ -23,7 +23,11 @@ namespace net
 			return;
 		}
 
-		on_message(*message);
+		// Are we sufficiently authenticated to handle this message?
+		if (get_access_level() >= message->get_access_level())
+			on_message(*message);
+		else
+			on_invalid_message();
 		delete message;
 	}
 }

src/protocol/net/Session.cpp

@@ -182,10 +182,8 @@ namespace net
 		// whether this is a control packet or not
 		if (header.is_control())
 			on_control_message(header);
-		else if (m_established)
-			on_application_message(header);
 		else
-			close();
+			on_application_message(header);
 	}
 }
 }