yes i know that.

Port number 1521 is th default port, but additional to that, i saw that ports 8080 and 2100 are opened by the listener too.

this is a part of the output of netstat -lntp of my Linux:

tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN 5594/tnslsnr
tcp 0 0 0.0.0.0:1521 0.0.0.0:* LISTEN 5594/tnslsnr
tcp 0 0 0.0.0.0:2100 0.0.0.0:* LISTEN 5594/tnslsnr

there is 8080 and 2100 ports too.

the question was why that other ports are opened?

thanks