How to determine the application listening to a particular port

How to determine the application listening to a particular port | LinuxWebLog.com

For example, I run nmap and find that port 712 is open:

712/tcp open unknown

But it's easily identified:

# fuser 712/tcp
712/tcp: 2098

# ps -fp 2098
UID PID PPID C STIME TTY TIME CMD
root 22098 8999 0 Aug18 ? 22:33 /usr/etc/customd

# man -k customd
custom (1M) - Custom daemon