Module nfc 

NFC (Near Field Communication) virtual tag server.

NetGet emulates an NFC Forum Type 4 tag, which is defined as ISO 7816-4 APDU exchange over ISO-DEP. It cannot generate an RF field — no PC/SC reader can be driven into card-emulation mode — so the tag is reachable over a bound TCP socket instead, using the vsmartcard vpcd framing:

reader → tag:  u16 big-endian length | payload
tag → reader:  u16 big-endian length | payload

A payload of exactly one byte is a vpcd control code (00 power off, 01 power on, 02 reset, 04 request ATR); anything longer is a command APDU.

This is the same wire format src/server/usb/smartcard/ already speaks, and it is not a private invention: configured with DEVICENAME /dev/null:<host>:<port> the real vpcd ifdhandler connects out to a listening virtual card, so a host running pcscd sees this server as a genuine PC/SC reader with a card in it. A test, meanwhile, only has to write a length-prefixed APDU to the socket — no hardware, no daemon.

What the model controls

• nfc_server_started → set_atr, set_ndef_message configure the tag.
• nfc_tag_selected (SELECT by AID) and nfc_apdu_received (every other APDU) → respond_to_apdu supplies the response body and status word.

Nothing is answered by hardcoded card logic: there is no file system and no stored NDEF parser here, only the state the model itself set. If no handler produces a response the tag replies 6F00 (fail closed), never a success; if the backend itself failed it replies 6400 when that backend is merely saturated, so a reader retries instead of recording a broken card.

Re-exports

pub use actions::NfcServerProtocol;

Modules

actions

NFC (Near Field Communication) server protocol actions.

apdu

ISO 7816-4 command APDU parsing for the virtual NFC Forum Type 4 tag.

Structs

NfcServer

NFC virtual tag server.

Constants

MAX_FRAME_LEN

Largest frame accepted from a reader. Bounds the read buffer so a hostile length prefix cannot make the server allocate.