nc -vz -w 2 地址 端口，命令如下：
nc -vz -w 2 www.idreamyou.cn 80
结果：
Connection to www.idreamyou.cn port 80 [tcp/http] succeeded!
不返回结果或者卡住说明端口不通
nc -vz -w 2 地址 端口，命令如下：
nc -vz -w 2 www.idreamyou.cn 80
结果：
Connection to www.idreamyou.cn port 80 [tcp/http] succeeded!
不返回结果或者卡住说明端口不通