本人花费半年的时间总结的《Java面试指南》已拿腾讯等大厂offer，已开源在github ，欢迎star！
来源：ggjucheng
www.cnblogs.com/ggjucheng
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
12345678910111213
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
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 2 210.34.6.89:telnet 210.34.6.96:2873 ESTABLISHED
tcp 296 0 210.34.6.89:1165 210.34.6.84:netbios-ssn ESTABLISHED
tcp 0 0 localhost.localdom:9001 localhost.localdom:1162 ESTABLISHED
tcp 0 0 localhost.localdom:1162 localhost.localdom:9001 ESTABLISHED
tcp 0 80 210.34.6.89:1161 210.34.6.10:netbios-ssn CLOSE
Active UNIX domain sockets (w/o servers)
Proto RefCnt Flags Type State I-Node Path
unix 1 [ ] STREAM CONNECTED 16178 @000000dd
unix 1 [ ] STREAM CONNECTED 16176 @000000dc
unix 9 [ ] DGRAM 5292 /dev/log
unix 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
-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
123456789
# netstat -a | moreActive Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 localhost:30037 *:* LISTENudp 0 0 *:bootpc *:*Active UNIX domain sockets (servers and established)Proto RefCnt Flags Type State I-Node Pathunix 2 [ ACC ] STREAM LISTENING 6135 /tmp/.X11-unix/X0unix 2 [ ACC ] STREAM LISTENING 5140 /var/run/acpid.socket
netstat -a | more
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 localhost:30037 : LISTEN
udp 0 0 *:bootpc :
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node Path
unix 2 [ ACC ] STREAM LISTENING 6135 /tmp/.X11-unix/X0
unix 2 [ ACC ] STREAM LISTENING 5140 /var/run/acpid.socket
列出所有 tcp 端口 netstat -at
1234567
# netstat -atActive Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 localhost:30037 *:* LISTENtcp 0 0 localhost:ipp *:* LISTENtcp 0 0 *:smtp *:* LISTENtcp6 0 0 localhost:ipp [::]:* LISTEN
netstat -at
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 localhost:30037 : LISTEN
tcp 0 0 localhost:ipp : LISTEN
tcp 0 0 :smtp : LISTEN
tcp6 0 0 localhost:ipp [::]: LISTEN
列出所有 udp 端口 netstat -au
123456
# netstat -auActive Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address Stateudp 0 0 *:bootpc *:*udp 0 0 *:49119 *:*udp 0 0 *:mdns *:*
netstat -au
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
udp 0 0 *:bootpc :
udp 0 0 *:49119 :
udp 0 0 *:mdns :
2、列出所有处于监听状态的 Sockets
只显示监听端口 netstat -l
123456
# netstat -lActive Internet connections (only servers)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 localhost:ipp *:* LISTENtcp6 0 0 localhost:ipp [::]:* LISTENudp 0 0 *:49119 *:*
netstat -l
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 localhost:ipp : LISTEN
tcp6 0 0 localhost:ipp [::]:* LISTEN
udp 0 0 *:49119 :
只列出所有监听 tcp 端口 netstat -lt
123456
# netstat -ltActive Internet connections (only servers)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 localhost:30037 *:* LISTENtcp 0 0 *:smtp *:* LISTENtcp6 0 0 localhost:ipp [::]:* LISTEN
netstat -lt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 localhost:30037 : LISTEN
tcp 0 0 :smtp : LISTEN
tcp6 0 0 localhost:ipp [::]: LISTEN
只列出所有监听 udp 端口 netstat -lu
12345
# netstat -luActive Internet connections (only servers)Proto Recv-Q Send-Q Local Address Foreign Address Stateudp 0 0 *:49119 *:*udp 0 0 *:mdns *:*
netstat -lu
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
udp 0 0 *:49119 :
udp 0 0 *:mdns :
只列出所有监听 UNIX 端口 netstat -lx
1234567
# netstat -lxActive UNIX domain sockets (only servers)Proto RefCnt Flags Type State I-Node Pathunix 2 [ ACC ] STREAM LISTENING 6294 private/maildropunix 2 [ ACC ] STREAM LISTENING 6203 public/cleanupunix 2 [ ACC ] STREAM LISTENING 6302 private/ifmailunix 2 [ ACC ] STREAM LISTENING 6306 private/bsmtp
netstat -lx
Active UNIX domain sockets (only servers)
Proto RefCnt Flags Type State I-Node Path
unix 2 [ ACC ] STREAM LISTENING 6294 private/maildrop
unix 2 [ ACC ] STREAM LISTENING 6203 public/cleanup
unix 2 [ ACC ] STREAM LISTENING 6302 private/ifmail
unix 2 [ ACC ] STREAM LISTENING 6306 private/bsmtp
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
12345678910111213141516171819
# netstat -sIp:total packets receivedwith invalid addressesforwardedincoming packets discardedincoming packets deliveredrequests sent outIcmp:ICMP messages receivedinput ICMP message failed.Tcp:active connections openingsfailed connection attemptsconnection resets receivedUdp:packets receivedpackets to unknown port received......
netstat -s
Ip:
total packets received
with invalid addresses
forwarded
incoming packets discarded
incoming packets delivered
requests sent out
Icmp:
ICMP messages received
input ICMP message failed.
Tcp:
active connections openings
failed connection attempts
connection resets received
Udp:
packets received
packets to unknown port received.
…..
显示 TCP 或 UDP 端口的统计信息 netstat -st 或 -su
12
# netstat -st # netstat -su
netstat -st
netstat -su
4、在 netstat 输出中显示 PID 和进程名称 netstat -p
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。
12345
# netstat -ptActive Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program nametcp 1 0 ramesh-laptop.loc:47212 192.168.185.75:www CLOSE_WAIT 2109/firefoxtcp 0 0 ramesh-laptop.loc:52750 lax:www ESTABLISHED 2109/firefox
netstat -pt
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 1 0 ramesh-laptop.loc:47212 192.168.185.75:www CLOSE_WAIT 2109/firefox
tcp 0 0 ramesh-laptop.loc:52750 lax:www ESTABLISHED 2109/firefox
5、在 netstat 输出中不显示主机，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。
同样可以加速输出，因为不用进行比对查询。
1
# netstat -an
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
123
# netsat -a --numeric-ports# netsat -a --numeric-hosts# netsat -a --numeric-users
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
12345678
# netstat -cActive Internet connections (w/o servers)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 ramesh-laptop.loc:36130 101-101-181-225.ama:www ESTABLISHEDtcp 1 1 ramesh-laptop.loc:52564 101.11.169.230:www CLOSINGtcp 0 0 ramesh-laptop.loc:43758 server-101-101-43-2:www ESTABLISHEDtcp 1 1 ramesh-laptop.loc:42367 101.101.34.101:www CLOSING^C
netstat -c
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 ramesh-laptop.loc:36130 101-101-181-225.ama:www ESTABLISHED
tcp 1 1 ramesh-laptop.loc:52564 101.11.169.230:www CLOSING
tcp 0 0 ramesh-laptop.loc:43758 server-101-101-43-2:www ESTABLISHED
tcp 1 1 ramesh-laptop.loc:42367 101.101.34.101:www CLOSING
^C
7、显示系统不支持的地址族 (Address Families)
1
netstat --verbose
netstat –verbose
在输出的末尾，会有如下的信息
1234
netstat: no support for `AF IPX' on this system.netstat: no support for `AF AX25' on this system.netstat: no support for `AF X25' on this system.netstat: no support for `AF NETROM' on this system.
netstat: no support for
AF IPX' on this system. netstat: no support for AF AX25’ on this system.
netstat: no support for
AF X25' on this system. netstat: no support for AF NETROM’ on this system.
8、显示核心路由信息 netstat -r
123456
# netstat -rKernel IP routing tableDestination Gateway Genmask Flags MSS Window irtt Iface192.168.1.0 * 255.255.255.0 U 0 0 0 eth2link-local * 255.255.0.0 U 0 0 0 eth2default 192.168.1.1 0.0.0.0 UG 0 0 0 eth2
netstat -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth2
link-local * 255.255.0.0 U 0 0 0 eth2
default 192.168.1.1 0.0.0.0 UG 0 0 0 eth2
注意： 使用 netstat -rn 显示数字格式，不查询主机名称
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。
123
# netstat -ap | grep sshtcp 1 0 dev-db:ssh 101.174.100.22:39213 CLOSE_WAIT -tcp 1 0 dev-db:ssh 101.174.100.22:57643 CLOSE_WAIT -
netstat -ap | grep ssh
tcp 1 0 dev-db:ssh 101.174.100.22:39213 CLOSE_WAIT -
tcp 1 0 dev-db:ssh 101.174.100.22:57643 CLOSE_WAIT -
找出运行在指定端口的进程
1
# netstat -an | grep ':80'
netstat -an | grep ‘:80’
10、显示网络接口列表
123456
# 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 0 0 0 0 0 0 0 0 BMUeth2 1500 0 26196 0 0 0 26883 6 0 0 BMRUlo 16436 0 4 0 0 0 4 0 0 0 LRU
netstat -i
Kernel Interface table
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1500 0 0 0 0 0 0 0 0 0 BMU
eth2 1500 0 26196 0 0 0 26883 6 0 0 BMRU
lo 16436 0 4 0 0 0 4 0 0 0 LRU
显示详细信息，像是 ifconfig 使用 netstat -ie:
123456789
# netstat -ieKernel Interface tableeth0 Link encap:Ethernet HWaddr 00:10:40:11:11:11UP BROADCAST MULTICAST MTU:1500 Metric:1RX packets:0 errors:0 dropped:0 overruns:0 frame:0TX packets:0 errors:0 dropped:0 overruns:0 carrier:0collisions:0 txqueuelen:1000RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)Memory:f6ae0000-f6b00000
netstat -ie
Kernel Interface table
eth0 Link encap:Ethernet HWaddr 00:10:40:11:11:11
UP BROADCAST MULTICAST MTU:1500 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:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Memory:f6ae0000-f6b00000
11、IP和TCP分析
查看连接某服务端口最多的的IP地址
1234567891011
wss8848@ubuntu:~$ netstat -nat | grep "192.168.1.15:22" |awk '{print $5}'|awk -F: '{print $1}'|sort|uniq -c|sort -nr|head -20221.136.168.36154.74.45.24278.173.31.23662.183.207.98192.168.1.14182.48.111.215124.193.219.34119.145.41.2114.255.41.3075.102.11.99wss8848@ubuntu:~$ netstat -nat | grep “192.168.1.15:22” |awk ‘{print $5}’|awk -F: ‘{print $1}’|sort|uniq -c|sort -nr|head -20
221.136.168.36
154.74.45.242
78.173.31.236
62.183.207.98
192.168.1.14
182.48.111.215
124.193.219.34
119.145.41.2
114.255.41.30
75.102.11.99
TCP各种状态列表
12345678
wss8848@ubuntu:~$ netstat -nat |awk '{print $6}'established)ForeignLISTENTIME_WAITESTABLISHEDTIME_WAITSYN_SENTwss8848@ubuntu:~$ netstat -nat |awk ‘{print $6}’
established)
Foreign
LISTEN
TIME_WAIT
ESTABLISHED
TIME_WAIT
SYN_SENT
先把状态全都取出来,然后使用uniq -c统计，之后再进行排序
123456789
wss8848@ubuntu:~$ netstat -nat |awk '{print $6}'|sort|uniq -cESTABLISHEDFIN_WAIT1ForeignLAST_ACKLISTENSYN_SENTTIME_WAITestablished)wss8848@ubuntu:~$ netstat -nat |awk ‘{print $6}’|sort|uniq -c
ESTABLISHED
FIN_WAIT1
Foreign
LAST_ACK
LISTEN
SYN_SENT
TIME_WAIT
established)
最后的命令如下：
1
netstat -nat |awk '{print $6}'|sort|uniq -c|sort -rnnetstat -nat |awk ‘{print $6}’|sort|uniq -c|sort -rn
分析access.log获得访问前10位的ip地址
1
awk '{print $1}' access.log |sort|uniq -c|sort -nr|head -10awk ‘{print $1}’ access.log |sort|uniq -c|sort -nr|head -10
关注后端技术精选，每天推送优质好文
