NETSTAT - useful command line utility to check connection formation

 NETSTAT is command line utility in Windows and Linux Operating systems that provides a way to verify whether TCP/IP parameters are working and connections are being formed. 

Netstat utility provides TCP and UDP protocol information and it becomes very essential in diagnosing the network and application association issues. 

Below command shows connection is being successfully formed from IP address 12.123.12.34 and is able to listen on 100.101.102.103 on port 1521 

[oracle@instance_name~]$ netstat -anp --tcp --udp   | grep 12.123.12.34
tcp        0      0 100.101.102.103:1521    12.123.12.34:56007      ESTABLISHED -
[oracle@siscebsdev ~]$

 

Below command shows connection is not being successfully formed from IP address 12.123.12.99 and is not able to listen on 100.101.102.103 on port 1521 

[oracle@instance_name~]$ netstat -anp --tcp --udp   | grep 12.123.12.99
[oracle@instance_name~]$