Get a file from TFTP server and download to stm32f4xx flash

Hello,

I enabled etherent and lwip ,tftp on my code. After I got tftp_server.c/.h files, Any body could help me to use this function or I have to do different. 

Actually I am upgrading my device firmware. To do that I want to download firmware from a TFTP server and store in user flash.

please help to get this done. any code that I can refer..