I am debugging ImageCaptureCore to communicate with external cameras. When I called the PTP function below to send a command and add data, the response timed out for more than 5 seconds. After waiting for a period of time, I obtained the response. However, the response callback function obtained responsivData.length as zero and ptpResponseData.length as zero too. (void)requestSendPTPCommand:(NSData *)ptpCommand outData:(NSData *)ptpData completion:(void (^)(NSData *responseData, NSData *ptpResponseData, NSError *error))completion; data is below: Wrote 1 = 0x1 bytes PTP：send data: (hexdump of 1 bytes) [ ] I/PTP (14564): 0000 01 - .