3.0 KiB
Simplex.FileTransfer.Client.Main
XFTP CLI client: send, receive, delete files with parallel chunk operations and web URI encoding.
Source: FileTransfer/Client/Main.hs
Non-obvious behavior
1. Web URI encoding: base64url(deflate(YAML))
encodeWebURI compresses the YAML-encoded file description with raw DEFLATE, then base64url-encodes the result. decodeWebURI reverses this. The compressed description goes in the URL fragment (after #), which is never sent to the router — the file description stays client-side.
2. CLI receive accepts both file paths and URLs
getInputFileDescription checks if the input starts with http:// or https://. If so, it extracts the URL fragment, decodes it via decodeWebURI, and uses the resulting file description. Otherwise, it reads a YAML file from disk. This allows receiving files via web links without a browser.
3. Redirect chain depth limited to 1
receive tracks a depth parameter starting at 1. After following one redirect, depth becomes 0. A second redirect throws "Redirect chain too long". This prevents infinite redirect loops from malicious file descriptions.
4. Parallel data packet uploads with router grouping
uploadFile groups data packets by router via groupAllOn, then uses pooledForConcurrentlyN 16 to process up to 16 router-groups concurrently. Within each group, data packets are uploaded sequentially (mapM). Errors from any upload are collected and the first one is thrown.
5. Random router selection
getXFTPServer selects a random router from the provided list for each chunk. With a single router, it's deterministic. With multiple routers, it uses StdGen in a TVar for thread-safe random selection via stateTVar.
6. withReconnect nests retry with reconnection
withReconnect wraps withRetry twice: the outer retry reconnects to the router, and the inner operation runs against the connection. On failure, the router connection is explicitly closed before retrying, forcing a fresh connection on the next attempt.
7. withRetry rejects zero retries
withRetry' 0 returns an "internal: no retry attempts" error. withRetry' 1 executes the action once without retry. This off-by-one convention means retryCount = 3 (the default) gives 3 total attempts (1 initial + 2 retries).
8. File description auto-deletion prompt
After successful receive or delete, removeFD either auto-deletes the file description (if --yes flag) or prompts the user. This prevents accidental reuse of one-time file descriptions — each receive consumes the description by ACKing data packets on the router.
9. Sender description uses first replica's router
createSndFileDescription takes the router from the first replica of each chunk for the sender's FileChunkReplica. This reflects the current limitation that each data packet is uploaded to exactly one router — the sender description records that single router.