To help you better understand the issue, here is a bit of a primer about IPv4 and IPv6 and translating between them:
IPv4 and IPv6 are basically two different ways to do internet. IPv4 is older and generally more widely used, but the newer IPv6 is becoming more popular every year due, largely out of necessity due to scalability issues of IPv4. Still, software support and experience is typically lagging behind for IPv6.
The problem with IPv4 and IPv6 is that they are incompatible. If you have an IPv6 connection, you can only talk to other computers on IPv6, and the same is true for IPv4. For this reason, many systems support both IPv4 and IPv6 so they can connect to services using either protocol.
However, your internet connection only supports IPv6, not IPv4. But our hosting platform only supports IPv4, not IPv6. So they cannot talk directly. This creates a bit of a problem.
Your ISP, Three, knows that many sites and services don’t support IPv6 yet. So they have setup a big router somewhere centrally, and all traffic that’s supposed to go to an IPv4 destination from their IPv6 customers is sent there. Using that router, Three can forward the IPv6 connection to your home to an IPv4 connection to our servers.
But any time network translation needs to happen (like switching between IPv4 and IPv6), there is the chance for things to get mangled, mislabeled or lost. And it would seem that Three did something in their big router that causes your FTP connection to get messed up.
I don’t know. I’m pretty sure that it’s related to their IPv6-to-IPv4 gateway. But I’m not an internet provider, so my knowledge about the subject is limited to that such gateways exists and what their purpose is. I have no idea how you would set something like that up, let alone how to avoid this specific issue.
I doubt that. The IPv6-to-IPv4 translation is done somewhere at Three. And they most likely just don’t provide IPv4 connectivity to your home, so there is nothing that can be done on the router side.
The FTP server from 000webhost.com appears to support IPv6 natively. So you can just connect to it over IPv6, and avoid the network translation.