Hi Group, I''ve just read the blog Henry referred to earlier: http://www.igvita.com/2008/05/27/ruby-eventmachine-the-speed-demon/ When I started looking at EM the "reactor pattern" was quite a new approach to thinking about my code, and posed a small barrier. I also note on rubyeventmachine.org there is a ''procedural implementation'' milestone, and perhaps the following relates? After some time I realized that since I was creating a class for each message that had its own build or parse method, I could use Aquarium (aquarium.rubyforge.org) to easily create methods: before_<in_msg_klass>, after_<in_msg_klass>, before_<out_msg_klass>, after_<out_msg_klass>. I find this observer (aspect oriented?) pattern allows me to write my code in a way that feels a little more like I''m used to, of course I still need to take care that the message sequence is unbroken. However, I haven''t yet seen the description ''observer oriented'' or ''aspect orient'' pattern used to describe writing EM applications. Any reasons why? I do wonder if ''performance issues'' are the reason? Hopefully someone else finds Aquarium useful. I should note there is a ''trap for young players'': Reusable aspects are achieved by ''include''ing at the _end_ of the class definition! Aquarium has "Preliminary support for advising Java classes in JRuby", however I have not used this. Dean Wampler has also been very helpful, responsive, patient and generally friendly. Cheers Mark