How to find ports opened by process ID in Linux?

netstat --all --program | grep '3265'

• --all show listening and non-listening sockets.
  
• --program show the PID and name of the program to which socket belongs.

You could also use a port scanner such as Nmap.

You can use the command below:

lsof -i -P |grep pid

As a side note, netstat -ao will read the /proc/PID/tcp etc to see the ports opened by the process. This means that its reading information supplied by the system (the linux KERNEL), and is in no way directly looking on the network interface or other means.Same goes for lsof.

If you are doing this as a security measure, you failed. You should never (NEVER EVER) trust the output of netstat, even if you are 100% sure you are in fact running a real netstat program (as opposed to a trojaned version) or any other program that reads the /proc filesystem. Some people seem to think that netstat, ls, ps or any other of the standard unix tools do some sort of magic and poll information from the sources, the truth is all of them rely on the /proc filesystem to get all of their data, which can be easily subverted by a rootkit or hypervisor.