功能说明：Netstat用于显示与IP、TCP、UDP和ICMP协议相关的统计数据，一般用于检验本机各端口的网络连接情况。
语 法：netstat [-acCeFghilMnNoprstuvVwx][-A<网络类型>][--ip]
补充说明：利用netstat指令可让你得知整个Linux系统的网络情况。
参 数：
-a或–all 显示所有连线中的Socket。
-A<网络类型>或–<网络类型> 列出该网络类型连线中的相关地址。
-c或–continuous 持续列出网络状态。
-C或–cache 显示路由器配置的快取信息。
-e或–extend 显示网络其他相关信息。
-F或–fib 显示FIB。
-g或–groups 显示多重广播功能群组组员名单。
-h或–help 在线帮助。
-i或–interfaces 显示网络界面信息表单。
-l或–listening 显示监控中的服务器的Socket。
-M或–masquerade 显示伪装的网络连线。
-n或–numeric 直接使用IP地址，而不通过域名服务器。
-N或–netlink或–symbolic 显示网络硬件外围设备的符号连接名称。
-o或–timers 显示计时器。
-p或–programs 显示正在使用Socket的程序识别码和程序名称。
-r或–route 显示Routing Table。
-s或–statistice 显示网络工作信息统计表。
-t或–tcp 显示TCP传输协议的连线状况。
-u或–udp 显示UDP传输协议的连线状况。
-v或–verbose 显示指令执行过程。
-V或–version 显示版本信息。
-w或–raw 显示RAW传输协议的连线状况。
-x或–unix 此参数的效果和指定”-A unix”参数相同。
–ip或–inet 此参数的效果和指定”-A inet”参数相同
netstat 的一些常用选项
netstat -s
本选项能够按照各个协议分别显示其统计数据。如果我们的应用程序（如Web浏览器）运行速度比较慢，或者不能显示Web页之类的数据，那么我们就可以用本选项来查看一下所显示的信息。我们需要仔细查看统计数据的各行，找到出错的关键字，进而确定问题所在。
1: [root@SM155 proc]# netstat -s
2: Ip:
3: 8530928 total packets received
4: 0 forwarded
5: 0 incoming packets discarded
6: 6972819 incoming packets delivered
7: 8521573 requests sent out
8: 1 fragments dropped after timeout
9: 39629 reassemblies required
10: 19667 packets reassembled ok
11: 1 packet reassembles failed
12: Icmp:
13: 16023 ICMP messages received
14: 175 input ICMP message failed.
15: ICMP input histogram:
16: destination unreachable: 4362
17: echo requests: 11661
18: 19476 ICMP messages sent
19: 0 ICMP messages failed
20: ICMP output histogram:
21: destination unreachable: 7815
22: echo replies: 11661
23: Tcp:
24: 1651264 active connections openings
25: 159526 passive connection openings
26: 197 failed connection attempts
27: 150104 connection resets received
28: 31 connections established
29: 6439010 segments received
30: 6739834 segments send out
31: 423 segments retransmited
32: 0 bad segments received.
33: 1649444 resets sent
34: Udp:
35: 135397 packets received
36: 7341 packets to unknown port received.
37: 0 packet receive errors
38: 1762263 packets sent
39: TcpExt:
40: ArpFilter: 0
41: 800 TCP sockets finished time wait in fast timer
42: 300 time wait sockets recycled by time stamp
43: 8850 delayed acks sent
44: 1 delayed acks further delayed because of locked socket
45: Quick ack mode was activated 12 times
46: 552580 packets directly queued to recvmsg prequeue.
47: 296789 packets directly received from prequeue
48: 724223 packets header predicted
49: 11117 packets header predicted and directly queued to user
50: TCPPureAcks: 249691
51: TCPHPAcks: 1235152
52: TCPRenoRecovery: 0
53: TCPSackRecovery: 1
54: TCPSACKReneging: 0
55: TCPFACKReorder: 0
56: TCPSACKReorder: 0
netstat -e
本选项用于显示关于以太网的统计数据。它列出的项目包括传送的数据报的总字节数、错误数、删除数、数据报的数量和广播的数量。这些统计数据既有发送的数据报数量，也有接收的数据报数量。这个选项可以用来统计一些基本的网络流量）。
1: [root@SM155 proc]# netstat -e
2: Active Internet connections (w/o servers)
3: Proto Recv-Q Send-Q Local Address Foreign Address State User Inode
4: tcp 0 0 10.90.243.155:49182 10.90.243.27:32931 ESTABLISHED root 382858
5: tcp 0 0 localhost.localdomain:49176 localhost.localdomain:39918 ESTABLISHED root 24542
6: tcp 1 0 10.90.243.155:64766 10.90.243.27:951 CLOSE_WAIT root 3239351
7: tcp 0 0 localhost.localdomain:39015 localhost.localdomain:49178 ESTABLISHED root 24546
8: tcp 0 0 localhost.localdomain:39016 localhost.localdomain:49179 ESTABLISHED root 24548
9: tcp 0 0 10.90.243.155:ssh 10.88.22.243:3672 ESTABLISHED root 6062002
netstat -r
本选项可以显示关于路由表的信息，类似于后面所讲使用route print命令时看到的 信息。除了显示有效路由外，还显示当前有效的连接。
1: [root@SM155 proc]# netstat -r
2: Kernel IP routing table
3: Destination Gateway Genmask Flags MSS Window irtt Iface
4: 10.90.243.0 * 255.255.255.0 U 0 0 0 eth0
5: 10.10.10.0 * 255.255.255.0 U 0 0 0 eth1
6: 169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
7: default 10.90.243.1 0.0.0.0 UG 0 0 0 eth0
8: [root@SM155 proc]#
netstat -a
本选项显示一个所有的有效连接信息列表，包括已建立的连接（ESTABLISHED），也包括监听连接请（LISTENING）的那些连接。
1: [root@SM155 proc]# netstat -a
2: Active Internet connections (servers and established)
3: Proto Recv-Q Send-Q Local Address Foreign Address State
4: tcp 0 0 10.90.243.155:39010 *:* LISTEN
5: tcp 0 0 *:shell *:* LISTEN
6: tcp 0 0 10.90.243.155:39011 *:* LISTEN
7: tcp 0 0 *:39012 *:* LISTEN
8: tcp 0 0 *:39015 *:* LISTEN
9: tcp 0 0 *:49159 *:* LISTEN
10: tcp 0 0 localhost.localdomain:39016 *:* LISTEN
11: tcp 0 0 *:49166 *:* LISTEN
12: tcp 0 0 *:39918 *:* LISTEN
13: tcp 0 0 *:sunrpc *:* LISTEN
14: tcp 0 0 *:49173 *:* LISTEN
15: tcp 0 0 *:ftp *:* LISTEN
16: tcp 0 0 *:ssh *:* LISTEN
17: tcp 0 0 *:13819 *:* LISTEN
18: tcp 0 0 *:2812 *:* LISTEN
19: tcp 0 0 10.90.243.155:49182 *:* LISTEN
20: tcp 0 0 10.90.243.155:49182 10.90.243.27:32931 ESTABLISHED
21: tcp 0 0 localhost.localdomain:49176 localhost.localdomain:39918 ESTABLISHED
22: tcp 1 0 10.90.243.155:64766 10.90.243.27:951 CLOSE_WAIT
23: tcp 0 0 localhost.localdomain:39015 localhost.localdomain:49178 ESTABLISHED
24: tcp 0 0 localhost.localdomain:39016 localhost.localdomain:49179 ESTABLISHED
netstat -n
显示所有已建立的有效连接。
1: [root@SM155 proc]# netstat -n
2: Active Internet connections (w/o servers)
3: Proto Recv-Q Send-Q Local Address Foreign Address State
4: tcp 0 0 10.90.243.155:49182 10.90.243.27:32931 ESTABLISHED
5: tcp 0 0 127.0.0.1:49176 127.0.0.1:39918 ESTABLISHED
6: tcp 1 0 10.90.243.155:64766 10.90.243.27:951 CLOSE_WAIT
7: tcp 0 0 127.0.0.1:39015 127.0.0.1:49178 ESTABLISHED
8: tcp 0 0 127.0.0.1:39016 127.0.0.1:49179 ESTABLISHED
9: tcp 0 0 127.0.0.1:39918 127.0.0.1:49176 ESTABLISHED
10: tcp 0 0 10.90.243.155:58692 10.90.243.155:39010 ESTABLISHED
11: tcp 0 0 10.90.243.155:39012 10.90.243.155:49168 ESTABLISHED
12: tcp 0 0 127.0.0.1:39012 127.0.0.1:49174 ESTABLISHED
13: tcp 0 0 10.90.243.155:39012 10.90.243.155:49175 ESTABLISHED
14: tcp 0 0 127.0.0.1:39012 127.0.0.1:49160 ESTABLISHED
15: tcp 0 0 10.90.243.155:39012 10.90.243.155:49161 ESTABLISHED
16: tcp 0 0 127.0.0.1:39012 127.0.0.1:49167 ESTABLISHED
17: tcp 0 0 10.90.243.155:49185 10.90.243.155:39011 ESTABLISHED
18: tcp 0 0 127.0.0.1:49174 127.0.0.1:39012 ESTABLISHED
19: tcp 0 0 10.90.243.155:49175 10.90.243.155:39012 ESTABLISHED
20: tcp 0 0 10.90.243.155:49168 10.90.243.155:39012 ESTABLISHED
21: tcp 0 0 127.0.0.1:49167 127.0.0.1:39012 ESTABLISHED
22: tcp 0 0 127.0.0.1:49160 127.0.0.1:39012 ESTABLISHED
23: tcp 0 0 10.90.243.155:49161 10.90.243.155:39012 ESTABLISHED
24: tcp 0 0 10.90.243.155:49159 10.90.243.155:58726 ESTABLISHED
25: tcp 0 0 127.0.0.1:49178 127.0.0.1:39015 ESTABLISHED
■ 原文网址：http://txw1958.cnblogs.com/