[lwip-users] Download a file for firmware upgrade

[Giuseppe Modugno]

I have a device running lwip stack and httpd server. The device has an 
external 2MB SPI Flash memory. The CPU is a microcontroller with 512kB 
internal Flash.

I'd like to upgrade the firmware (the internal Flash memory) by download 
the new binary from Internet. The user can check the presence of a new 
firmware version through the web pages answered from httpd.

When the user activates the remote upgrade, the device should download 
the binary file from a server and save it to the external Flash memory. 
After a reboot, the bootloader detects the new firmware on the external 
memory and copy it to the internal Flash memory.

Now I don't know how to download a file from Internet. FTP client? HTTP 
client? Any other protocol? I'd like to use a standard server (FTP, 
HTTP, ...), anyway this isn't a must.

Please, give me a suggestion. Thank you.