[Boost-users] [Asio] How can you detect port collsions?

Hi All Thanks to those of you who have answered my previous asio queries - I'm gradually gaining on the problems! I am allocating port numbers on tcp connections dynamically, and must allocate and reserve the port number without blocking. I also have multiple instances of the process which needs to do this, and I'm plagued by port collisions. How do I detect, and avoid, port number collsions? Thanks, Rob.