UDP

How it works

TFTP adds its own stop-and-wait on UDP. QUIC adds encryption and retransmission on UDP. A raw UDP file copy that neither side designed will drop bytes silently. File transfer on UDP means one of those designed protocols.

A phone boots with TFTP over UDP and retries a lost 512-byte block. A browser downloads the same day over HTTP/3, which is QUIC over UDP, and a lost packet stalls one stream. Neither is 'UDP file transfer' as a raw send.

How it differs

UDP is not faster by itself. It is less reliable until a protocol above it repairs loss.

Firewalls that block UDP 443 force HTTP/3 to fall back. The file still moves.

Allow the fallback.

On the ticket

• The practical close is a log line: time, actor, byte count, result.
• Without that line the transfer is a story.
• With it, the next person can see whether this door did what the ticket claimed.
• If the path is shared, say so in the partner profile so a later change does not silently pick a different limit, key, or region.
• On a real ticket, write down the door, the byte count, and the clock.
• For udp, that means naming the host or bucket, the expected size, and the time the other side must have a complete file.
• A progress bar is not that record.
• A 200 response that arrives before the complete call is not that record.
• If a retry is allowed, say how many and whether it resumes.
• If a person must approve the send, name the person.
• Partners who receive udp files should match on hash or size before they import.
• A same-length corrupt file passes a size check and fails a hash.
• Keep the published hash off the only channel an attacker can edit, or treat it as a corruption check rather than a substitution check.
• When the path changes, new key, new region, new cap, update the profile the same day so the next run does not use a stale limit.