you can use at framework to send/recv data in socket API
example: see examples\tcp_through_module_based_at_socket
project: see board\TencentOS_tiny_EVB_MX_Plus\KEIL\tcp_through_module_based_at_socket
1. the address in tos_hal_sd_*(tos_hal_sd.c) is by byte, but address in HAL_SD_WriteBlocks/HAL_SD_ReadBlocks is by sector
2. convert address in tos_hal_sd_* from byte to sector( / 512)