When you connect to a FTP server you can receive the following message

227 Entering Passive Mode (192,168,0,14,243,121)

The first 4 digits are the IP address you have to connect to (192.168.0.1)

The last 2 digits are used to calculate the passive port. (243*256)+121=62329

So this message actually means: connect to 192.168.0.1 over port 62329

This is how passive mode works.