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.
sudo 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