gen_tcp:close/1
关闭一个 TCP 套接字
用法：
close(Socket) -> ok
关闭一个 TCP 套接字。
{Rand, _RandSeed} = random:uniform_s(9999, erlang:now()),
Port = 40000 + Rand,
case gen_tcp:listen(Port, [binary, {packet, 0}, {active, false}]) of
{ok, Socket} ->
gen_tcp:close(Socket);
_ ->
socket_listen_fail
end.