例如尝试连接到谷歌的邮件服务器。
root@mail2:~# nc -vC 209.85.232.26 smtp
Connection to 209.85.232.26 25 port [tcp/smtp] succeeded!
220 mx.google.com ESMTP u65si15520060qkf.84 - gsmtp
_
root@mail2:~# nc -vC 2607:f8b0:400d:c0a::1a smtp
_
它只是挂在那儿。
我的 ifconfig -
root@mail2:~# ifconfig
eth0 Link encap:Ethernet HWaddr b2:94:3b:b0:8c:35
inet addr:104.131.80.101 Bcast:104.131.127.255 Mask:255.255.192.0
inet6 addr: 2604:a880:800:10::1a40:e001/64 Scope:Global
inet6 addr: fe80::b094:3bff:feb0:8c35/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1