Hi, I need to send ip information of a client to the other one (as they will connect to each other directly now). I used async echo server sample http://www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/echo/async_...as a starting point. I guess sessions are recorded in io_service instance, since in the server constructor when we create session, we pass io_service to it. session* new_session = new session(io_service_); Can I get information of connected sessions from io_service? (or any other recommendations on how to better design it?) To expand my question: I am implementing a chat server, but the chats will not go over the server (is it a bad idea?). many clients connects, I keep their status (online or not) in a database. when A wants to talk to B, I need to pass request to B, how can I get a handle to my connection to B while I am in the instance of session with A? I am still not sure I understand io_service concept. Is this proactor thing similar to observer pattern? When we pass io_service as a parameter to something, are we registering it to be observed in io_service? Thanks in advance, (*Thanks for all the previous answers too, *I have made significant progress...) Best regards, Ozgur (Oscar) Ozturk www.DrOzturk.com Phone: +1 (908) DROZGUR i.e, +1 (908) 376-9487