said by WayOutback :port 443
Internet file formats are defined by
RFC2046.
I'm sure ports can be blocked, but it may also be possible to block file types. Last I knew, they used Cisco equipment on their Exede system
Port 443 has two uses, one for Hypertext Transfer Protocol over TLS/SSL (HTTPS), and for QUIC (from Chromium) for HTTPS, which is
explained here for Google.
Since hypertext is like viewing a text-based web page, its possible Exede does not block that dual function port.
Btw, Vannevar Bush wrote "As We May Think" in 1945 in which he described his conception of the Memex (which we now call hypertext).