January 2006, Issue 186

Portable Web Server
Renesas M16C Design Contest 2005 Entry

DYNAMIC DNS CLIENT

One of my portable web server’s best features is its ability to appear as a static web site on the Internet, even though the IP address is dynamically reassigned each time the PPP client connects to the ISP. This is achieved using a dynamic DNS service (e.g., www.dynu.com), which provides a simple and free automated interface for resolving DNS queries and points them to the web server.

The mechanism for informing the dynamic DNS service of the assigned IP address consists of an HTTP GET request to its main server. The request contains the domain name, the assigned IP address, and a security password. The dynamic DNS client within the web site module has a periodic timer that opens a socket to the main server and sends the GET request every few minutes.