Cybersecurity

I wrote a perl socket program which listens on 40011 port number the program works fine. But just a question crossed in my mind I tried to find the answer but I didn't find. Please if anyone have the answer or idea please reply...

How to know that which ports are bocked on the UNIX (HP-UX) system?

How to know that the port is already in use so we can avoid its reuse?


Thanks..

depending on what you mean by blocked. if you have firewall sitting in between that HPUX machine and other parts of your network, you can verify your firewall rules. however if you want to know which ports are "blocked" while you are logged into the HPUX machine, you can use netstat and grep for LISTEN state. eg

Code:

netstat -an |grep -w LISTEN

. If the port num you are looking for is not there, it means the application that is using that port is not started. ( however, you cannot assume its blocked in the context of a firewall). An application that havn't started doesn't really mean its blocked by a firewall. To find the port already in use, you can use the netstat method, or lsof command eg.

Code:

 lsof -i tcp:40001

all ports below 1024 are blocked for non root users....

u can check the port status by using netstat command

netstat -an |grep <PORT_NO>