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
[vagrant@centos6 ~]$ netstat|moreActive Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address ??????????????Foreign Address ????????????Statetcp ???????0 ?????0 10.0.2.15:ssh ??????????????10.0.2.2:52091 ?????????????ESTABLISHEDActive UNIX domain sockets (w/o servers)Proto RefCnt Flags ??????Type ??????State ????????I-Node Pathunix ?11 ????[ ] ????????DGRAM ???????????????????11021 ?/dev/logunix ?2 ?????[ ] ????????DGRAM ???????????????????11556 ?@/org/freedesktop/hal/udev_eventunix ?2 ?????[ ] ????????DGRAM ???????????????????8986 ??@/org/kernel/udev/udevdunix ?3 ?????[ ] ????????STREAM ????CONNECTED ????17777unix ?3 ?????[ ] ????????STREAM ????CONNECTED ????17776
从整体上看，netstat的输出结果可以分为两个部分：
OUTPUT ??Active Internet connections (TCP, UDP, raw) ??Proto ??????The protocol (tcp, udp, raw) used by the socket. ??Recv-Q ??????The count of bytes not copied by the user program connected to this socket. ??Send-Q ??????The count of bytes not acknowledged by the remote host.
一个是Active Internet connections，称为有源TCP连接，其中"Recv-Q"和"Send-Q"指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，这种情况非常少见。
Active UNIX domain Sockets ??Proto ??????The protocol (usually unix) used by the socket. ??RefCnt ??????The reference count (i.e. attached processes via this socket). ??Flags ??????The ?flags ?displayed ?is ?SO_ACCEPTON ?(displayed as ACC), SO_WAITDATA (W) or SO_NOSPACE (N). ?SO_ACCECPTON is used on ??????unconnected sockets if their corresponding processes are waiting for a connect request. The other flags are not of nor- ??????mal interest. ??Type ??????There are several types of socket access: ??????SOCK_DGRAM ?????????????The socket is used in Datagram (connectionless) mode. ??????SOCK_STREAM ?????????????This is a stream (connection) socket. ??????SOCK_RAW ?????????????The socket is used as a raw socket.
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数量，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，netstat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。(重要)-l 仅列出有在 Listen (监听) 的服務状态-p 显示建立相关链接的程序名(macOS中表示协议 -p protocol)-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 (重要)-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列出所有tcp端口: ?netstat -at列出所有udp端口: ?netstat -au
2. 列出所有处于监听状态的 Sockets
只显示监听端口: ?????????netstat -l只列出所有监听tcp端口: ??netstat -lt只列出所有监听udp端口: ??netstat -lu只列出所有监听UNIX端口: ?netstat -lx
3. 显示每个协议的统计信息
显示所有端口的统计信息 netstat -s
[vagrant@centos6 ~]$ netstat -sIp:total packets receivedwith invalid addressesforwardedincoming packets discardedincoming packets deliveredrequests sent outIcmp:ICMP messages receivedinput ICMP message failed. ???ICMP input histogram:ICMP messages sentICMP messages failed ???ICMP output histogram:Tcp:active connections openingspassive connection openingsfailed connection attemptsconnection resets receivedconnections establishedsegments receivedsegments send outsegments retransmitedbad segments received.resets sentUdp:packets receivedpackets to unknown port received.packet receive errorspackets sentUdpLite:TcpExt:delayed acks sentpackets directly queued to recvmsg prequeue.packets header predictedacknowledgments not containing data receivedpredicted acknowledgmentsTCP data loss eventsIpExt: ???InOctets: 146500 ???OutOctets: 132340
显示 TCP 或 UDP 端口的统计信息 netstat -st 或 -su
# netstat -st # netstat -su
4. 显示 PID 和进程名称
netstat -p 可以与其它开关一起使用，就可以添加 “PID/进程名称” 到 netstat 输出中，这样 debugging 的时候可以很方便的发现特定端口运行的程序。
[root@centos6 ~]# netstat -ptActive Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address ??????????????Foreign Address ????????????State ??????PID/Program nametcp ???????0 ?????0 10.0.2.15:ssh ??????????????10.0.2.2:52964 ?????????????ESTABLISHED 3008/sshdtcp ???????0 ?????0 10.0.2.15:ssh ??????????????10.0.2.2:52091 ?????????????ESTABLISHED 2813/sshd
5. 不显示主机，端口和用户名 (host, port or user)
当你不想让主机，端口和用户名显示，使用 netstat -n。将会使用数字代替那些名称。该参数可以加速output的输出，因为不用进行比对查询。
# netstat -an# 如果只是不想让这三个名称中的一个被显示，使用以下命令# netsat -a --numeric-ports# netsat -a --numeric-hosts# netsat -a --numeric-users
6. 持续输出 netstat 信息
netstat 将每隔一秒输出网络信息。
# netstat -t -c 2
7. 显示系统不支持的地址族 (Address Families)
netstat --verbose
8. 显示核心路由信息
[root@centos6 ~]# netstat -rnKernel IP routing tableDestination ????Gateway ????????Genmask ????????Flags ??MSS Window ?irtt Iface10.0.2.0 ???????0.0.0.0 ????????255.255.255.0 ??U ????????0 0 ?????????0 eth0169.254.0.0 ????0.0.0.0 ????????255.255.0.0 ????U ????????0 0 ?????????0 eth00.0.0.0 ????????10.0.2.2 ???????0.0.0.0 ????????UG ???????0 0 ?????????0 eth0# 注意： 使用 netstat -rn 显示数字格式，不查询主机名称，效果等价于route -n
9. 找出程序运行的端口
并不是所有的进程都能找到，没有权限的会不显示，使用 root 权限查看所有的信息。
[root@centos6 ~]# netstat -apn | grep sshtcp ???????0 ?????0 0.0.0.0:22 ?????????????????0.0.0.0:* ??????????????????LISTEN ?????1438/sshdtcp ???????0 ?????0 10.0.2.15:22 ???????????????10.0.2.2:52964 ?????????????ESTABLISHED 3008/sshdtcp ???????0 ?????0 10.0.2.15:22 ???????????????10.0.2.2:52091 ?????????????ESTABLISHED 2813/sshdtcp ???????0 ?????0 :::22 ??????????????????????:::* ???????????????????????LISTEN ?????1438/sshdunix ?3 ?????[ ] ????????STREAM ????CONNECTED ????18443 ?3008/sshdunix ?3 ?????[ ] ????????STREAM ????CONNECTED ????18442 ?3011/sshdunix ?2 ?????[ ] ????????DGRAM ???????????????????18439 ?3008/sshdunix ?3 ?????[ ] ????????STREAM ????CONNECTED ????17777 ?2813/sshdunix ?3 ?????[ ] ????????STREAM ????CONNECTED ????17776 ?2816/sshdunix ?2 ?????[ ] ????????DGRAM ???????????????????17773 ?2813/sshd
找出运行在指定端口的进程
[root@centos6 ~]# netstat -an | grep ‘:22‘tcp ???????0 ?????0 0.0.0.0:22 ?????????????????0.0.0.0:* ??????????????????LISTENtcp ???????0 ?????0 10.0.2.15:22 ???????????????10.0.2.2:52964 ?????????????ESTABLISHEDtcp ???????0 ?????0 10.0.2.15:22 ???????????????10.0.2.2:52091 ?????????????ESTABLISHEDtcp ???????0 ?????0 :::22 ??????????????????????:::* ???????????????????????LISTEN
10. 显示网络接口列表
[root@centos6 ~]# netstat -iKernel Interface tableIface ??????MTU Met ???RX-OK RX-ERR RX-DRP RX-OVR ???TX-OK TX-ERR TX-DRP TX-OVR Flgeth0 ??????1500 ??0 ???12125 ?????0 ?????0 ?????0 ????5474 ?????0 ?????0 ?????0 BMRUlo ???????65536 ??0 ???????0 ?????0 ?????0 ?????0 ???????0 ?????0 ?????0 ?????0 LRU[root@centos6 ~]# netstat -ieKernel Interface tableeth0 ?????Link encap:Ethernet ?HWaddr 52:54:00:5D:A4:AF ?????????inet addr:10.0.2.15 ?Bcast:10.0.2.255 ?Mask:255.255.255.0 ?????????inet6 addr: fe80::5054:ff:fe5d:a4af/64 Scope:Link ?????????UP BROADCAST RUNNING MULTICAST ?MTU:1500 ?Metric:1 ?????????RX packets:12131 errors:0 dropped:0 overruns:0 frame:0 ?????????TX packets:5477 errors:0 dropped:0 overruns:0 carrier:0 ?????????collisions:0 txqueuelen:1000 ?????????RX bytes:7474852 (7.1 MiB) ?TX bytes:580343 (566.7 KiB)lo ???????Link encap:Local Loopback ?????????inet addr:127.0.0.1 ?Mask:255.0.0.0 ?????????inet6 addr: ::1/128 Scope:Host ?????????UP LOOPBACK RUNNING ?MTU:65536 ?Metric:1 ?????????RX packets:0 errors:0 dropped:0 overruns:0 frame:0 ?????????TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 ?????????collisions:0 txqueuelen:0 ?????????RX bytes:0 (0.0 b) ?TX bytes:0 (0.0 b)
11. IP和TCP分析
查看连接某服务端口最多的的IP地址/TCP各种状态列表:
http://www.cnblogs.com/echo1937/p/6646208.html
转 : https://www.cnblogs.com/echo1937/p/6677325.html
Linux netstat命令详解
原文地址：https://www.cnblogs.com/fps2tao/p/10313711.html