Linux netstat命令详解

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|more
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State
tcp        0      0 10.0.2.15:ssh               10.0.2.2:52091              ESTABLISHED
Active UNIX domain sockets (w/o servers)
Proto RefCnt Flags       Type       State         I-Node Path
unix  11     [ ]         DGRAM                    11021  /dev/log
unix  2      [ ]         DGRAM                    11556  @/org/freedesktop/hal/udev_event
unix  2      [ ]         DGRAM                    8986   @/org/kernel/udev/udevd
unix  3      [ ]         STREAM     CONNECTED     17777
unix  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 -s
Ip:
    2081 total packets received
    2 with invalid addresses
    0 forwarded
    0 incoming packets discarded
    2079 incoming packets delivered
    1319 requests sent out
Icmp:
    0 ICMP messages received
    0 input ICMP message failed.
    ICMP input histogram:
    0 ICMP messages sent
    0 ICMP messages failed
    ICMP output histogram:
Tcp:
    0 active connections openings
    3 passive connection openings
    0 failed connection attempts
    0 connection resets received
    1 connections established
    1957 segments received
    1103 segments send out
    0 segments retransmited
    0 bad segments received.
    1 resets sent
Udp:
    122 packets received
    0 packets to unknown port received.
    0 packet receive errors
    216 packets sent
UdpLite:
TcpExt:
    9 delayed acks sent
    1 packets directly queued to recvmsg prequeue.
    730 packets header predicted
    5 acknowledgments not containing data received
    1036 predicted acknowledgments
    0 TCP data loss events
IpExt:
    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 -pt
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 10.0.2.15:ssh               10.0.2.2:52964              ESTABLISHED 3008/sshd
tcp        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 -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.0.2.0        0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth0
0.0.0.0         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 ssh
tcp        0      0 0.0.0.0:22                  0.0.0.0:*                   LISTEN      1438/sshd
tcp        0      0 10.0.2.15:22                10.0.2.2:52964              ESTABLISHED 3008/sshd
tcp        0      0 10.0.2.15:22                10.0.2.2:52091              ESTABLISHED 2813/sshd
tcp        0      0 :::22                       :::*                        LISTEN      1438/sshd
unix  3      [ ]         STREAM     CONNECTED     18443  3008/sshd
unix  3      [ ]         STREAM     CONNECTED     18442  3011/sshd
unix  2      [ ]         DGRAM                    18439  3008/sshd
unix  3      [ ]         STREAM     CONNECTED     17777  2813/sshd
unix  3      [ ]         STREAM     CONNECTED     17776  2816/sshd
unix  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:*                   LISTEN
tcp        0      0 10.0.2.15:22                10.0.2.2:52964              ESTABLISHED
tcp        0      0 10.0.2.15:22                10.0.2.2:52091              ESTABLISHED
tcp        0      0 :::22                       :::*                        LISTEN

10. 显示网络接口列表

[root@centos6 ~]# 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    12125      0      0      0     5474      0      0      0 BMRU
lo        65536   0        0      0      0      0        0      0      0      0 LRU

[root@centos6 ~]# netstat -ie
Kernel Interface table
eth0      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

 

参考资料:http://www.cnblogs.com/ggjucheng/archive/2012/01/08/2316661.html

posted @ 2017-04-07 11:32  又是火星人  阅读(62393)  评论(2编辑  收藏  举报