On some systems, PASSV mode FTP doesn't work correctly. There are PTFs for this starting with IBM i v6r1. For earlier releases, you have 2 options, both involve disabling FTP passive mode.
Option 1: During the FTP session, disable Passive Mode by typing in the following FTP command:
Option 2: The first option can be problematic if you are forgetful. An alternative is to create a couple of Data Areas. if these data areas exist when an FTP session is started, the passive modes are disabled.
CRTDTAARA DTAARA(QUSRSYS/QTMFTPPASV) TYPE(*LGL) AUT(*USE) CRTDTAARA DTAARA(QUSRSYS/QTMFTPEPSV) TYPE(*LGL) AUT(*USE)
Now when FTP is started, both Passive and Extended Passive modes are automatically disabled.
Remember, the data area method is nice because it applies system-wide to all new FTP sessions without having to sign off/on the system.
There is also a suggestion to turn off Extended Port, to do that, create the following data area:
CRTDTAARA DTAARA(QUSRSYS/QTMFTPEPRT) TYPE(*LGL) AUT(*USE)
Disables EPORT if PTF SI33243 is also installed, unless on v6r1 or later, then only the data area is needed.