I was looking at needing to do a large number of reverse DNS lookups for a log analysis program I am writing, and wanted to use some form of async lookup to speed the program up (vs. doing each look up in series, at a couple of seconds per lookup). boost::asio and the async_resolve functions looked to be just what I wanted, BUT: I can find no good examples of a simple lookup. By "simple" I mean "given an address, give me the host name(s) associated with that address". All the examples were for a lookup by host name/transport type/port, e.g. host name/tcp/80. In my case I neither need a port # nor even have one - I just want the RDNS for the address. It seems to me the documentation in the boost::asio is a bit light on the various types for resolver queries, endpoint types, and such - and seems to be more focused on TCP and UDP than generic IP. Are there any better examples out there of RDNS using boost::asio?