The DNS Server has the "hosts.txt" file that will have a hostname on each line with its corresponding IP. When the Server starts, the lines of the "hosts.txt" file will be read and its recordings will be registered in the Hashtable. After if receives a request from a client and there is no name in the Hashtable then it will use the methods of InetAddress in order to resolve the name to ip, which it will register in the Hashtable and in addition will add it (append) at the end of the "hosts.txt" file.

1) Compile & Run Server

-> javac Dns_Server.java

-> java Dns_Server

2) Compile & Run Client (in different command line window)

-> javac Dns_Client.java

-> java Dns_Client

After type a domain name to resolve it to IP Address