Check if the port is open

Check if the localhost port is enabled

1. It is obvious that the service has been enabled, but it cannot be used. You need to check whether the port is enabled. netstat command

   Options:

   -r list routing table

   -n do not perform ip and host resolution

   -a list all link states

   -t tcp

   -in udp

   -l listen

   -p list filenames of pid and program

   
   

   
   

   [root@www ~]# netstat -tulnp | grep 1187

   tcp        0      0 0.0.0.0:139                 0.0.0.0:*                   LISTEN      1187/smbd

   tcp        0      0 0.0.0.0:445                 0.0.0.0:*                   LISTEN      1187/smbd

   tcp        0      0 :::139                      :::*                        LISTEN      1187/smbd

   tcp        0      0 :::445                      :::*                        LISTEN      1187/smbd

2. Use the telnet command to check whether the local port is enabled

   
   

   [root@www ~]# telnet localhost 25

       Trying ::1...

       Connected to localhost.

       Escape character is '^]'.

       220 www.localdomain ESMTP Postfix

       ^]

       telnet> quit

       Connection closed.

Detecting whether the remote host port is open is also the telnet command

[root@www ~]# telnet 10.107.230.18 80

Trying 10.107.230.18...

Connected to 10.107.230.18.

Escape character is '^]'.

^]

telnet> quit

Connection closed