(1) 查看服务端口是否启用。常用于查看服务器进程端口是否启动

[[email?protected] ~]# netstat -nlp |grep 21050
tcp6       0      0 :::21050                :::*                    LISTEN      10859/impalad

(2) 查看端口连接情况

[[email?protected] ~]# netstat -nat|grep -i "21050"    不带进程号
tcp6       0      0 :::21050                :::*                    LISTEN     
tcp6       0      0 192.168.11.124:21050    192.168.11.126:32474    ESTABLISHED
tcp6       0      0 192.168.11.124:21050    192.168.11.126:64128    ESTABLISHED

[[email?protected] ~]#  netstat -natp|grep -i "21050"   带进程号
tcp6       0      0 :::21050                :::*                    LISTEN      6334/impalad        
tcp6       0      0 192.168.11.126:14792    192.168.11.124:21050    ESTABLISHED 24236/java          
tcp6       0      0 192.168.11.126:32566    192.168.11.124:21050    ESTABLISHED 15111/java

(3) 统计端口的连接数

[[email?protected] ~]# netstat -nat|grep -i "21050" |wc -l
63

二、netstat命令help

[[email?protected] ~]# netstat --help   查看命令帮助
usage: netstat [-vWeenNcCF] [<Af>] -r         netstat {-V|--version|-h|--help}
       netstat [-vWnNcaeol] [<Socket> ...]
       netstat { [-vWeenNac] -I[<Iface>] | [-veenNac] -i | [-cnNe] -M | -s [-6tuw] } [delay]
   -r,--route              display routing table
    -I,--interfaces=<Iface> display interface table for <Iface>
    -i,--interfaces         display interface table
    -g,--groups             display multicast group memberships
    -s,--statistics         display networking statistics (like SNMP)
    -M,--masquerade         display masqueraded connections

    -v,--verbose            be verbose
    -W,--wide               don‘t truncate IP addresses
    -n,--numeric            don‘t resolve names
    --numeric-hosts          don‘t resolve host names
    --numeric-ports          don‘t resolve port names
    --numeric-users          don‘t resolve user names
    -N,--symbolic           resolve hardware names
    -e,--extend             display other/more information
    -p,--programs           display PID/Program name for sockets    显示进程号
    -o,--timers             display timers
    -c,--continuous         continuous listing

    -l,--listening          display listening server sockets   服务端listen
    -a,--all                display all sockets (default: connected)   显示所有sockets
    -F,--fib                display Forwarding Information Base (default)
    -C,--cache              display routing cache instead of FIB
    -Z,--context            display SELinux security context for sockets
    <Socket>={-t|--tcp} {-u|--udp} {-U|--udplite} {-S|--sctp} {-w|--raw}

##            {-x|--unix} --ax25 --ipx --netrom