Activate the tftp server on your Mac:

To change the properties, edit the file

/System/Library/LaunchDaemons/tftp.plist

The default directory is /private/tftpboot.

Make this directory accessible for everybody.

chmod 777 /private/tftpboot

and start it with

sudo launchctl load -F /System/Library/LaunchDaemons/tftp.plist

If you want to stop the daemon, do

sudo launchctl unload /System/Library/LaunchDaemons/tftp.plist