what tcp ports used by ftp?

[Woolie Willie]

I am using the ftp commands in the inet toolkit. It has been working fine. Recently my server has been under attack from internet hackers. I had to put Zone Alarm on the PC for protection. Now I get pop-ups from zone alarm when my client tries to access ftp. The ports it is reporting are 1056,1059, and 1062. Seems to be different each time. I thought FTP ran on port 20 and 21. What ports do I need to open????

[Jeremiah Cox]

Hello Willie,
It sounds as though you are using passive FTP when you should be using active FTP. With active FTP, only ports 20 and 21 are used on the server; however, there can be issues if the client is behind a firewall because the server uses port 20 to connect back to the client for data transfers. In passive FTP, the client connects to port 21 on the server, tells it PASV, then the FTP server tells the client an unprivileged port that the client connects to on the server (1024+, not 20). I think this is what is upsetting your firewall software. I hope this helps you out.

Jeremiah Cox
Applications Engineer
National Instruments
http://www.ni.com/ask