http://i3xi5qxvbrngh3g6o7czwjfxwjzigook7zxzjmgwg5b7xnjcn5hzciad.onion/socks-extensions
In response to a RESOLVE_PTR SOCKS5 command with
an IPv4 address as its target, Tor attempts to find the canonical
hostname for that IPv4 record, and returns it in the “server bound
address” portion of the reply.
(This command was not supported before Tor 0.1.2.2-alpha.) HTTP-resistance Tor checks the first byte of each SOCKS request to see whether it looks
more like an HTTP request (that is, it starts with a “G”, “H”, or “P”).