Hi all, I am just beginning to learn how to use Boost Asio in a multithreaded environment, and one thing struck me when looking at the various examples. I have not been able to find an answer to this in the documentation, but in case it is explained somewhere that I've missed I apologize in advance. Taking the asynchronous echo server as my base I am writing a multithreaded server that handles connections in a thread pool. My question is simply, why is the io_service object always passed around between class instances as a reference in the constructor? Why can one not store it as a global variable? I cannot see how this makes a difference, and a global seems to make things a lot easier. Is there a particular reason why I should not do this? Thanks in advance for any help. Kind regards, Philip Bennefall