Linux common commands you will really see what --netstat port

First, use the netstat command to view port usage

(1) review the service port is enabled. Commonly used to view the server process port is started

[root@cdh-003 ~]# netstat -nlp |grep 21050
tcp6       0      0 :::21050                :::*                    LISTEN      10859/impalad 

(2) Check port connections

[root@cdh-003 ~]# 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

[root@cdh-005 ~]#  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) port connection statistics

[root@cdh-003 ~]# netstat -nat|grep -i "21050" |wc -l
63

Two, netstat command help

[root@cdh-003 ~]# 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