usestd::net::{TcpListener};// adding a Socket9ExtSo to gain access to functions.
usesocket9::Socket9ExtSo;fnmain(){let tcp =TcpListener::bind("127.0.0.1:0").unwrap();// use from Socket9ExtSo
let proto = tcp.get_so_protocol().unwrap();println!("proto: {:?}", proto);}