BinkP

BinkP is the TCP/IP mailer protocol used by OxideBBS for FTN packet and bundle exchange. Caller file-transfer protocols such as XMODEM and ZMODEM are not used for network mail exchange.

The oxidebbs-binkp crate provides:

• command and data frame encoding/decoding with stream read/write helpers
• command constants for M_NUL, M_ADR, M_PWD, M_FILE, M_OK, M_EOB, M_GOT, M_ERR, M_BSY, M_GET, and M_SKIP
• client and server handshakes with address/password validation
• per-link password validation for inbound listener sessions
• TLS-required, TLS-opportunistic, and plaintext-legacy security planning
• TLS client and server socket helpers using TLS 1.2 or newer
• file offer, bounded data-frame send/receive, M_GOT, and M_EOB helpers
• batch send/receive helpers for empty polls, multi-file exchange, and large files
• retry policy and one-active-session-per-link guard primitives

net poll <link> opens a BinkP client session, sends pending outbound packet files, receives the peer batch into the inbound drop directory, marks acknowledged outbound packet rows processed, and writes network_poll_log rows. net poll --all repeats that workflow for enabled links.

TLS-required links attempt TLS and fail the poll if certificate validation or the TLS handshake fails. TLS-opportunistic links attempt TLS first and fall back to plaintext only when the link is explicitly legacy-compatible. Plaintext legacy links skip TLS and emit operator-visible warnings through the security preflight and poll-log surfaces.

The inbound BinkP listener accepts plaintext or TLS sockets, authenticates the remote address/password against enabled links, rejects plaintext sessions for TLS-required links before M_OK, writes received files into the selected network profile inbound drop directory, sends pending outbound files for the authenticated link, and marks DB-backed outbound packets processed after acknowledgement.

Only one active session per link is allowed inside each running poll/listener process. A second concurrent session for the same link is refused by the session guard.