O2 Tech support told me no ports are blocked over 4G - but then, the guy
I was talking to didn't know the difference between Active & Passive
Mode FTP, so I'm not hopeful. As to why FTP over 4G - well, when the
best vdsl connection you can get is 4.5...
I have exactly the same problem - TLS connections work fine over my vdsl
connection (also with O2) but not over 4G. No luck at all with O2 tech
support. And now it's started dropping FTP connections at random....
Anyone any suggestions?