用
The domain name queries carried out by gethostbyname() and
gethostbyaddr() use a combination of any or all of the
name server named(8), a broken out line from /etc/hosts,
and the Network Information Service (NIS or YP), depending
upon the contents of the order line in /etc/host.conf.
(See resolv+(8)). The default action is to query
named(8), followed by /etc/hosts.
得到对方的用户名称