Add README

README.md

+Simple DynDNS server
+====================
+
+This is a simple DynDNS server implementation that builds on the Knot DNS server.
+
+Features
+--------
+
+Register a new domain:
+
+```
+$ curl -4 'http://localhost:3000/register?domain=myname'
+{
+	"domainName":"myname.test.test",
+	"token":"ecf43b7659fc09d81c4b55ded31d6b0b",
+	"message":"DNS record is not served until first DynDNS update."
+}
+```
+
+Update DNS record:
+
+```
+curl -4 'http://localhost:3000/update?token=ecf43b7659fc09d81c4b55ded31d6b0b&ip=1.1.1.1'
+{
+	"message":"Updated."
+}
+```
+
+**WARNING: You need to use a proxy that handles authentication and authorization!**
+
+Dependencies
+------------
+
+- [Knot DNS server](https://www.knot-dns.cz/) - Open source DNS server developed by the Czech domain registrar
+- [MongoDB](https://www.mongodb.com/) - NoSQL database
+
+Running
+-------
+
+Setup: `npm install`
+
+`sudo node index.js`
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