ddclient is a Perl client used to update dynamic DNS entries for accounts on 'Dynamic DNS
Network Services' (DynDNS) free DNS service. It currently supports a lot of different
routers and a few different services.
ddclient fits excellent into the "Extracting Dynamic IP From China" scenario where the Chinese client IP address is known to the server through FTP uploads of images by a netcam ("NetCam gallery"). China's national firewall (Golden Shield Project) blocks access to services like DynDNS from within China and therefore the client IP address must be extracted via a server located outside China which then can update DynDNS entries.
While the server periodically extracts the IP address from the FTP log files and outputs it into a text file, ddclient reads the file and updates DynDNS as scheduled.
A simpler alternative tool could be inadyn-mt, which comes with installers for various systems and can be run from the command line in Linux as well. It's limited in file/web page data reading but for a basic use (local machine's IP address), it does the job.
