PTP/IP

PTP/IP is the variant of PTP designed to be used on TCP.

All packet types start with a length and type field. The layout of the rest of the fields depends on type.

A standard request to the responder is as follows:

1. Send Command request

struct PtpIpBulkContainer {
    uint32_t length;
    uint32_t type;
    uint32_t data_phase;
    uint16_t code;
    uint32_t transaction;
    uint32_t params[5]; 
};

Rules:

• Set length to 18 + (4 * number_of_params)
• Set type to PTPIP_COMMAND_REQUEST (0x6)
• Set the data_phase field to 2 if you are sending a data payload. Set to 1 if otherwise.
• Set code to a PTP_OC_ opcode.
• Set the transaction to the transaction ID for this operation.

2. Send Data Start packet

struct PtpIpStartDataPacket {
    uint32_t length;
    uint32_t type;
    uint32_t transaction;
    uint64_t payload_length;
};

Rules:

• Set length to 20.
• Set type to PTPIP_DATA_PACKET_START (0x9)
• Set transaction to the transaction ID for this operation.
• Set data_phase_length to the size of the payload in the following data packet.

3. Send Data End Packet

struct PtpIpEndDataPacket {
    uint32_t length;
    uint32_t type;
    uint32_t transaction;
    // payload data goes here
};

Rules:

• Set length to 12 + payload_length
• Set type to PTPIP_DATA_PACKET_END (0xc)
• Set data_phase_length to the size of the payload in the following data packet.
• Copy the payload that will be sent to the device at offset 12.

4. Responses

For an operation, you may get a data payload as a response (R->I)

The response to an operation will either be: - PTPIP_DATA_PACKET_START packet followed by PTPIP_DATA_PACKET_END, and finally a PTPIP_COMMAND_RESPONSE packet - Just a PTPIP_COMMAND_RESPONSE packet

Response Container

struct PtpIpResponseContainer {
    uint32_t length;
    uint32_t type;
    uint16_t code;
    uint32_t transaction;
    uint32_t params[5];
};