[Boost-users] Question about Protocols and boost::asio::ip::tcp::iostream

I am trying to put together a program that needs a very simple networking component, esentially just dumping a lot of data from iostreams into a socket, unformatted, and tcp::iostream looked perfect for it. I have a question about its usage though. Every example I've seen looks something like tcp::iostream s("server", "protocol"). So far I've seen "http" and "daytime" as protocols. I am wondering exactly where these constants are defined. Also, for my purposes, how hard would it be to extend a previously defined protocol (i.e. telnet) since all I really need to do is connect to a port of my choosing and dump data.