Why doesn't Megaphone's mobile Internet allow me to download a file from an FTP server?

Question

Mobile development

Comrades, the situation is as follows: we have developed a mobile application that, when launched, downloads an xml file with data from our ftp server (1.3 mb in size), converts it to jason and broadcasts the received data in the application interface.
We encountered a problem that when the application is launched on devices with a SIM card and mobile Internet from Megafon, the application cannot download the xml file, since Megafon blocks the incoming stream with data from the ftp server when trying to access it.
On devices with SIM cards of other operators, everything starts up and works successfully.
We sent an application to support Megafon - almost a week there is no answer.
Can anyone come across?

Answer 1

If the ftp port is standard, then the megaphone blocks it. like some others.
Change the port to something like - 21211

Answer 2

The megaphone could close the ports

Answer 3

And than the choice of ftp is caused?
Why not give over http through the same nginx? If authentication, then it is also in it. Also, it will be faster than ftp. You can also reap xml initially with anything and this will greatly save traffic. If xml changes often, then you can enable on-the-fly compression in nginx.
I do not quite understand why create a problem and then try to heroically solve it. Providers often cheat with non-HTTP traffic, i.e. they can block ftp\smtp and many other things, they can include the lowest priority for such traffic and a huge handful of other charms and not only for mobile operators. From here you can wind up with a mustache that using http traffic is simply safer for such cases. the chances of running into the jokes you cited are many times less.