Java Network Programming, Second Edition

The InetAddress Class

The java.net.InetAddress class is Java’s encapsulation of an IP address. It is used by most of the other networking classes, including Socket, ServerSocket, URL, DatagramSocket, DatagramPacket, and more.

public final class InetAddress extends Object implements Serializable

This class represents an Internet address as two fields: hostName (a String) and address (an int). hostName contains the name of the host; for example, www.oreilly.com. address contains the 32-bit IP address. These fields are not public, so you can’t access them directly. It will probably be necessary to change this representation to a byte array when 16-byte IPv6 addresses come into use. However, if you always use the InetAddress class to represent addresses, the changeover should not affect you; the class shields you from the details of how addresses are implemented.

Creating New InetAddress Objects

There are no public constructors in the InetAddress class. However, InetAddress has three static methods that return suitably initialized InetAddress objects, given a little information. They are:

public static InetAddress InetAddress.getByName(String hostName) 
 throws UnknownHostException
public static InetAddress[] InetAddress.getAllByName(String hostName) 
 throws UnknownHostException
public static InetAddress InetAddress.getLocalHost(  ) 
 throws UnknownHostException

All three of these may make a connection to the local DNS server to fill out the information in the InetAddress object. This has a ...