DynIP For Linux

DynIP is an embarrasingly-simple server and client purely for getting systematic updates of a client's IP address.

The client is typically configured to run on a schedule basis using crontab or Windows Scheduled Tasks. When launched, the client sends a UDP datagram to the server, with it's hostname in the data packet.

The server, when it receives the UDP datagram, opens a JSON file at the path specified in the CLIENT_LOG_PATH. The server looks to see if the client name (the data portion of the packet) is already in the list of known addresses. If it is, it updates the record with the new IP address from the packet header and the current date and time. If it is new, it adds it to the dict of known hosts.

To configure the server, edit dynip/server.py and modify the UDP_IP, UDP_PORT and CLIENT_LOG_PATH. Descriptions of each are in the code.

Then start the server by typing:

python dynip/server.py

To launch the client and have it fire off a UDP packet, edit dynip/client.py and modify the SERVER_HOSTNAME and SERVER_PORT lines. Descriptions of each are in the code.

Then launch the client by typing:

python dynip/client.py

The server will then save the hostname, ip address and date/time in the CLIENT_LOG_PATH file (dynip.json in the default configuration).

I am about to go on an extended trip away from home, yet need to know the dynamic IP address that is assigned to my home cable router so that I can easily help my family remotely in case they need help with their computers. In order to do this, I need to know the IP address that my cable provider as assigned to my cable modem.

By installing the client on each of my computers at home and triggering the client to run every 5 minutes, the server will always keep a log of the most recent public IP address of the boundary device.