How to find port opened by a process?

[root@server1 ~]# ps -eaf | grep  20927 
apache   20927  1740  0 03:32 ?        00:00:00 /usr/sbin/httpd


[root@server1 ~]# lsof -p 20927 -i -a
COMMAND   PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
httpd   20927 apache    5u  IPv6  11430      0t0  TCP *:http (LISTEN)
httpd   20927 apache    7u  IPv6  11434      0t0  TCP *:https (LISTEN)

How to find a PIDs using a port?

Simple solution: Use lsof :)

The following solution works perfectly on a Linux system. In case of Solaris, lsof has to be installed first because it is not a part of default OS.

[root@linux01 ~]# lsof -w -n -i tcp:22
COMMAND   PID   USER   FD   TYPE     DEVICE SIZE NODE NAME
sshd     2410   root    3u  IPv4       6134       TCP *:ssh (LISTEN)
sshd     1639   root    3u  IPv4 1637600475       TCP 10.20.30.99:ssh->10.20.50.231:35263 (ESTABLISHED)
sshd     9592   root    3u  IPv4 3266851044       TCP 10.20.30.99:ssh->10.20.50.231:44621 (ESTABLISHED)
sshd    10119   root    3u  IPv4 3006017510       TCP 10.20.30.99:ssh->10.20.50.231:62445 (ESTABLISHED)
sshd    13909   root    3u  IPv4  739010581       TCP 10.20.30.99:ssh->10.20.40.88:35215 (ESTABLISHED)
sshd    24696   root    3u  IPv4  273846126       TCP 10.20.30.99:ssh->10.20.40.89:39529 (ESTABLISHED)
sshd    24900   root    3u  IPv4  352035868       TCP 10.20.30.99:ssh->10.20.40.88:59163 (ESTABLISHED)
sshd    25662   root    3u  IPv4  982162556       TCP 10.20.30.99:ssh->10.20.40.89:65096 (ESTABLISHED)
sshd    27358   root    3u  IPv4  982169152       TCP 10.20.30.99:ssh->10.20.40.89:65097 (ESTABLISHED)