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OpenZCineOpenZCine

Connection spine

OpenZCine speaks standard PTP to Nikon Z bodies: PTP-IP over Wi-Fi, or PTP over the USB-C cable. There is no Bluetooth step and no vendor SDK. Every control, live-view frame and media byte rides the same serialized PTP session. Order of operations on Wi-Fi:

discover → TCP :15740 Init_Command → Init_Event → OpenSession → GetDeviceInfo → pair (first time) → app-control mode → live view → media
  1. Reach the camera. Join the camera’s own access point, share a router with it, or let it join the phone’s hotspot. Discovery browses Bonjour _ptp._tcp and probes the local subnet.
  2. Init handshake. Command socket first (Init_Command_Request / Init_Command_Ack), then the event socket with the connection number the camera assigned. Both on TCP port 15740.
  3. OpenSession. Transaction ID 0, then GetDeviceInfo. The operations the body advertises decide every later step, not the model name.
  4. Pairing (first time only). Gen-3 bodies show a four-digit code; the operator confirms it on both screens (GetPairingInfo, ConfirmPairing). USB-C and original Z 5 / Z 6 / Z 7 / Z 50 bodies have no pairing step: the cable, or joining the camera’s own network, is the trust boundary.
  5. App-control mode. ChangeApplicationMode on Gen-2 and Gen-3 bodies, a write of ApplicationMode (0xD1F0) on Gen 1. Over USB the ZR also needs ChangeCameraMode remote mode.
  6. Vendor discovery. GetVendorCodes (or GetVendorPropCodes on older bodies) lists the vendor properties the body can report, which gates polling.
  7. Live view and media run as ordinary transactions on the same command channel.

A saved camera skips pairing: the app runs a quiet profile probe, and if the app-control switch answers OK the session continues. A refusal or a hangup is treated as the camera’s word, and the app falls back to one fresh pairing.

Disconnects send CloseSession before closing the sockets, and a reconnect waits a short settle so the camera can release its single session slot. A body that never sees the old session end can refuse or wedge on a fast re-Init.

Implementation lives in Sources/OpenZCineCore/ (packets, handshake, policies) and the platform transports (OpenCine Sources/OpenCineNikon/PTPIPTransport.swift and USBCameraTransport.swift for iOS, OpenCine Sources/OpenCineNikonAndroid/ for Android). Platform shells own sockets, permissions and the Wi-Fi join. Body generations and per-model differences are in Nikon Z Devices.