【求助】FTP伺服器有問題

[bad]

我家中用HINET線路架一個SERU伺服器
在其他HINET線路都正常可以進入下載

但是在學校就不能，有封掉一些PORT，不管有沒有開啟PASV模式，都只能出現
[R] 220 Serv-U FTP-Server v2.5k for WinSock ready...
[R] USER XXX
[R] 331 User name okay, need password.
[R] PASS (hidden)
[R] 230 User logged in, proceed.
[R] SYST
[R] 215 UNIX Type: L8
[R] FEAT
[R] 500 'FEAT': command not understood.
[R] PWD
[R] 257 "/f:/" is current directory.
[R] TYPE A
[R] 200 Type set to A.
[R] PORT X.X.X.X,6,239
[R] 200 PORT Command successful.
[R] LIST -al
[R] 150 Opening ASCII mode data connection for /bin/ls.
我想是不是紅色那一航有問題~FTP不是都設定21PORT嗎？
他是不是用6239這個PORT來連啊??為什麼會這樣呢