-a ：all，表示列出所有的连接，服务监听，Socket资料
-t ：tcp，列出tcp协议的服务
-u ：udp，列出udp协议的服务
-n ：port number， 用端口号来显示
-l ：listening，列出当前监听服务
-p ：program，列出服务程序的PID(显示pid)
-c ： 持续的输出
-s : 显示统计信息
-i ：显示网络设备的信息(建议使用ifconfig命令得到更丰富的数据)

举例：

1. netstat

   
   image.png

2. 查看监听端口并显示pid

   
   image.png
3. 统计TCP处于每个状态的数目

netstat -ant | awk '$1~/tcp/{a[$6]++} END{for(i in a) print i,a[i]}'

image.png

4. 显示网络设备信息

   
   image.png
5. 显示统计信息

$netstat -s
Ip:
    11171317 total packets received
    0 forwarded
    0 incoming packets discarded
    11171317 incoming packets delivered
    10926797 requests sent out
Icmp:
    2499 ICMP messages received
    151 input ICMP message failed.
    ICMP input histogram:
        destination unreachable: 315
        timeout in transit: 180
        echo requests: 2004
    2007 ICMP messages sent
    0 ICMP messages failed
    ICMP output histogram:
        destination unreachable: 3
        echo replies: 2004
IcmpMsg:
        InType3: 315
        InType8: 2004
        InType11: 180
        OutType0: 2004
        OutType3: 3
Tcp:
    635225 active connections openings
    998235 passive connection openings
    2970 failed connection attempts
    165 connection resets received
    168 connections established
    11161584 segments received
    13571031 segments send out
    26505 segments retransmited
    4 bad segments received.
    21357 resets sent
Udp:
    7231 packets received
    3 packets to unknown port received.
    0 packet receive errors
    24552 packets sent
UdpLite:
TcpExt:
    10 invalid SYN cookies received
    1 resets received for embryonic SYN_RECV sockets
    1081835 TCP sockets finished time wait in fast timer
    155490 delayed acks sent
    367 delayed acks further delayed because of locked socket
    Quick ack mode was activated 62 times
    12730 packets directly queued to recvmsg prequeue.
    2301002 packets directly received from backlog
    47619146 packets directly received from prequeue
    1699670 packets header predicted
    37328 packets header predicted and directly queued to user
    3500729 acknowledgments not containing data received
    1806591 predicted acknowledgments
    58 times recovered from packet loss due to SACK data
    Detected reordering 3 times using FACK
    Detected reordering 2 times using SACK
    Detected reordering 12 times using time stamp
    1 congestion windows fully recovered
    12 congestion windows partially recovered using Hoe heuristic
    TCPDSACKUndo: 228
    66 congestion windows recovered after partial ack
    TCPLostRetransmit: 13
    1 timeouts in loss state
    184 fast retransmits
    7 forward retransmits
    88 retransmits in slow start
    9402 other TCP timeouts
    TCPLossProbes: 1326
    TCPLossProbeRecovery: 624
    3 sack retransmits failed
    62 DSACKs sent for old packets
    1815 DSACKs received
    3 connections reset due to unexpected data
    17 connections reset due to early user close
    263 connections aborted due to timeout
    TCPDSACKIgnoredNoUndo: 547
    TCPSpuriousRTOs: 15
    TCPSackShifted: 97
    TCPSackMerged: 131
    TCPSackShiftFallback: 276
    TCPRcvCoalesce: 260510
    TCPOFOQueue: 3253
    TCPChallengeACK: 4
    TCPSYNChallenge: 4
    TCPWantZeroWindowAdv: 6
    TCPSynRetrans: 23029
    TCPOrigDataSent: 7723106
    TCPHystartTrainDetect: 515
    TCPHystartTrainCwnd: 10849
    TCPHystartDelayDetect: 1
    TCPHystartDelayCwnd: 29
IpExt:
    InOctets: -1230225412
    OutOctets: -1341641495
    InNoECTPkts: 11171134
    InECT1Pkts: 4
    InECT0Pkts: 176
    InCEPkts: 3

参考

[netstat(http://www.cnblogs.com/peida/archive/2013/03/08/2949194.html)