NB-IOT模块M5311发送数据到服务器，本代码为C代码，基于STM32F1系列单片机，工程为keil5工程，可以此为模板修改。(Nb-iot module m5311 sends data to the server, this code is C code, based on stm32f1 series single chip microcomputer, the project is keil5 project, which can be modified as a template.)