Thanks! But I still have trouble to connect to the server. The following is what I got:
Status: Connecting to ftp.321211.net ...
Status: Connected with ftp.321211.net. Waiting for welcome message...
Response: 220 Serv-U FTP Server v5.0 for WinSock ready...
Command: USER linux
Response: 331 User name okay, need password.
Command: PASS *****
Response: 530 Not logged in.
Error: Unable to connect!