简介Netstat 命令用于显示各种网络相关信息，如网络连接，路由表，接口状态 (Interface Statistics)，masquerade 连接，多播成员 (Multicast Memberships) 等等 。
输出信息含义执行netstat后，其输出结果为
Active Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 2 210.34.6.89:telnet 210.34.6.96:2873 ESTABLISHEDtcp 296 0 210.34.6.89:1165 210.34.6.84:netbIOS-ssn ESTABLISHEDtcp 0 0 localhost.localdom:9001 localhost.localdom:1162 ESTABLISHEDtcp 0 0 localhost.localdom:1162 localhost.localdom:9001 ESTABLISHEDtcp 0 80 210.34.6.89:1161 210.34.6.10:netbios-ssn CLOSEActive UNIX domain sockets (w/o servers)Proto RefCnt Flags Type State I-Node Pathunix 1 [ ] STREAM CONNECTED 16178 @000000ddunix 1 [ ] STREAM CONNECTED 16176 @000000dcunix 9 [ ] DGRAM 5292 /dev/logunix 1 [ ] STREAM CONNECTED 16182 @000000df
从整体上看，netstat的输出结果可以分为两个部分：
一个是Active Internet connections，称为有源TCP连接，其中"Recv-Q"和"Send-Q"指%0A的是接收队列和发送队列 。这些数字一般都应该是0 。如果不是则表示软件包正在队列中堆积 。这种情况只能在非常少的情况见到 。
另一个是Active UNIX domain sockets，称为有源Unix域套接口(和网络套接字一样，但是只能用于本机通信，性能可以提高一倍) 。
Proto显示连接使用的协议,RefCnt表示连接到本套接口上的进程号,Types显示套接口的类型,State显示套接口当前的状态,Path表示连接到套接口的其它进程使用的路径名 。
常见参数-a (all)显示所有选项，默认不显示LISTEN相关
-t (tcp)仅显示tcp相关选项
-u (udp)仅显示udp相关选项
-n 拒绝显示别名，能显示数字的全部转化成数字 。
-l 仅列出有在 Listen (监听) 的服務状态
【Linux netstat命令详解】-p 显示建立相关链接的程序名
-r 显示路由信息，路由表
-e 显示扩展信息，例如uid等
-s 按各个协议进行统计
-c 每隔一个固定时间，执行该netstat命令 。
提示：LISTEN和LISTENING的状态只有用-a或者-l才能看到
实用命令实例 
1. 列出所有端口 (包括监听和未监听的)列出所有端口 netstat -a
Active Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 2 210.34.6.89:telnet 210.34.6.96:2873 ESTABLISHEDtcp 296 0 210.34.6.89:1165 210.34.6.84:netbios-ssn ESTABLISHEDtcp 0 0 localhost.localdom:9001 localhost.localdom:1162 ESTABLISHEDtcp 0 0 localhost.localdom:1162 localhost.localdom:9001 ESTABLISHEDtcp 0 80 210.34.6.89:1161 210.34.6.10:netbios-ssn CLOSEActive UNIX domain sockets (w/o servers)Proto RefCnt Flags Type State I-Node Pathunix 1 [ ] STREAM CONNECTED 16178 @000000ddunix 1 [ ] STREAM CONNECTED 16176 @000000dcunix 9 [ ] DGRAM 5292 /dev/logunix 1 [ ] STREAM CONNECTED 16182 @000000df列出所有 tcp 端口 netstat -at
# netstat -at Active Internet connections (servers and established) Proto Recv-Q Send-Q Local AddressForeign AddressState tcp00 localhost:30037*:*LISTEN tcp00 localhost:ipp*:*LISTEN tcp00 *:smtp*:*LISTEN tcp600 localhost:ipp[::]:*LISTEN列出所有 udp 端口 netstat -au
# netstat -au Active Internet connections (servers and established) Proto Recv-Q Send-Q Local AddressForeign AddressState udp00 *:bootpc*:* udp00 *:49119*:* udp00 *:mDNS*:* 
2. 列出所有处于监听状态的 Sockets只显示监听端口 netstat -l
# netstat -l Active Internet connections (only servers) Proto Recv-Q Send-Q Local AddressForeign AddressState tcp00 localhost:ipp*:*LISTEN tcp600 localhost:ipp[::]:*LISTEN udp00 *:49119*:*只列出所有监听 tcp 端口 netstat -lt
# netstat -lt Active Internet connections (only servers) Proto Recv-Q Send-Q Local AddressForeign AddressState tcp00 localhost:30037*:*LISTEN tcp00 *:smtp*:*LISTEN tcp600 localhost:ipp[::]:*LISTEN只列出所有监听 udp 端口 netstat -lu
# netstat -lu Active Internet connections (only servers) Proto Recv-Q Send-Q Local AddressForeign AddressState udp00 *:49119*:* udp00 *:mdns*:*只列出所有监听 UNIX 端口 netstat -lx
# netstat -lx Active UNIX domain sockets (only servers) Proto RefCnt FlagsTypeStateI-NodePath unix2[ ACC ]STREAMLISTENING6294private/maildrop unix2[ ACC ]STREAMLISTENING6203public/cleanup unix2[ ACC ]STREAMLISTENING6302private/ifmail unix2[ ACC ]STREAMLISTENING6306private/bsmtp3. 显示每个协议的统计信息显示所有端口的统计信息 netstat -s
# netstat -s Ip: 11150 total packets received 1 with invalid addresses 0 forwarded 0 incoming packets discarded 11149 incoming packets delivered 11635 requests sent out Icmp: 0 ICMP messages received 0 input ICMP message failed. Tcp: 582 active connections openings 2 failed connection attempts 25 connection resets received Udp: 1183 packets received 4 packets to unknown port received. .....