Detecting the IP Change

To determine whether a client should update, it must have a reliable method to determine what its current IP address is so it can compare the current address to the last updated address. There are two methods.

Internal Method

A client may determine, automatically or through the input of the user, that it is directly connected to the Internet. The device would have a publicly addressable IP address. In this case, the optimal method is to obtain the IP address from the operating system’s network stack.

Web IP Detection (CheckIP)

A client may determine, automatically or through the input of the user, that it is not directly connected to the Internet. The client is on a machine with a private IP, usually on RFC 1918 space (10/8, 172.16/12, 192.168/16). In this case, the optimal method is to use web IP detection.

Dyn.rs operates a CheckIP service which may be used with clients that work with DynDNS.

Update Requests

After a change in IP address has been detected or a user alters any of their settings, the client should perform an update. All updates are sent using a well-formed HTTP request. The system will pass back a return code in the response body that the client needs to parse.

The HTTP Request

Updates can be performed over HTTP or SSL/TLS-encrypted HTTPS (preferred).

All requests should be sent to hostname dyn.rs. Hard coding the IP address is not acceptable as the IP address may change.

The update interface listens on ports 80 and 8245 for HTTP, and 443 for HTTPS. Port 8245 may be used to bypass transparent HTTP proxies. It is not necessary to open any incoming ports (or allow incoming ICMP) for updating.

Examples

These examples are provided only as samples, for better understanding of the process.

Authentication in URL

For web-browsers or utility programs (fetch, curl, lwp-request) that can parse authentication section in URL.

https://{username}:{password}@dyn.rs/nic/update?hostname={hostname}&myip={IP Address}

Curl command-line example

curl -ks -u {username}:{password} "https://dyn.rs/nic/update/?hostname={hostname}&myip={IP Address}"

Raw HTTP GET Request

Actual HTTP request should look like following fragment. Note that there is the bare minimum set of headers. Request should be followed by sending an empty line.

Fragment base-64-authorization should be represented by Base 64 encoded username:password string.

GET /nic/update?hostname=yourhostname&myip=ipaddress HTTP/1.0
Host: dyn.rs
Authorization: Basic base-64-authorization
User-Agent: Company - Device - Version Number

Please note that both GET and POST requests are permitted and will be processed.

Update Parameters

   hostname=johndoe.dyn.rs
   hostname=-
or hostname=

   hostname=home.johndoe.dyn.rs
or hostname=home

Return Codes

When updating a hostname, the response to the update request will be one of the short return codes described below, followed by one space or tab character, and the appropriate message (everything after the first blank character to the end of the line). If there is an error, clients should communicate to the user a brief description of the problem that the return code indicates. All the return codes are given in the response body, with appropriate HTTP codes that indicate success (2xx), client error (4xx), or server error (5xx).

Update Types