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PTP-IP packet

Framing is in Sources/OpenZCineCore/PTPIPPacket.swift (self-tested). All integers are little-endian. Plaintext, no encryption on the link.

Layout

Section titled “Layout”
length:u32le | type:u32le | payload
Field Notes
length Whole packet, header included. Less than 8 is invalid.
type Packet type, below
payload Type-specific

Packet types

Section titled “Packet types”
Value Type Channel Notes
1 Init_Command_Request command 16-byte initiator GUID, UTF-16LE friendly name with NUL, protocol version 0x00010000
2 Init_Command_Ack command Connection number u32, then the camera’s name
3 Init_Event_Request event The connection number from the ack
4 Init_Event_Ack event Header only
5 Init_Fail either Reason: 1 rejected initiator, 2 busy, 3 unspecified
6 Operation_Request command See below
7 Operation_Response command See below
8 Event event See below
9 Start_Data command Transaction ID and total length of the data phase
0x0A Data command Transaction ID u32, then a chunk
0x0B Cancel command
0x0C End_Data command Transaction ID u32, then the last chunk
0x0D / 0x0E Probe_Request / Probe_Response event Header-only liveness ping. Answer it: a missing response lets the camera treat the host as dead and close the session.

Operation request

Section titled “Operation request”
dataPhase:u32le | opcode:u16le | transactionID:u32le | params:u32le × 0…5
dataPhase Meaning
1 No data phase, or data-in as accepted by the ZR
2 Data-out (host to camera)
3 Data-in (camera to host), the canonical value

OpenSession uses transaction ID 0. After that the transport assigns sequential IDs.

Operation response and event

Section titled “Operation response and event”
code:u16le | transactionID:u32le | params:u32le × n

The same shape serves Operation_Response (a response code such as 0x2001 OK) and Event (an event code such as 0x4006 DevicePropChanged). See the command catalog.

Data phase

Section titled “Data phase”

A data-in transaction arrives as Start_Data, zero or more Data, then End_Data, then Operation_Response. The collector strips the 4-byte transaction ID from each chunk and concatenates the rest. Real Nikon transactions are four packets or fewer; large objects are read in bounded partial reads.

USB container

Section titled “USB container”

Over USB-C the same operations ride PIMA 15740 generic containers instead (PTPUSBContainer.swift):

length:u32le | type:u16le | code:u16le | transactionID:u32le | payload
Type Meaning
1 Command
2 Data
3 Response
4 Event

The USB command container has no DataPhaseInfo field, and the operation, response or event code sits in the container header. One bulk read can carry part of a container or several containers, so a framing buffer vends exactly one validated container at a time. See transport.