Hallo Brian, Hello Jeremy I tried using the connection header but for some reasons the topic field "topic" does not exist! I have: callerid, latching, md5sum, message_definition, type. Currently I am using the Ubuntu 10.04 with the default package installation ros::M_string connection_header = event.getConnectionHeader(); for ( ros::M_string::iterator it=connection_header.begin() ; it != connection_header.end(); it++ ) std::cout << it->first << " => " << it->second << std::endl; That code shows me -----------> callerid => /camera0/image_proc latching => 0 md5sum => 1b5cf7f984c229b6141ceb3a955aa18f message_definition => # This message defines meta information for a camera. It should be in ........... type => sensor_msgs/CameraInfo Any hints? Greetings Markus