Network Clients - Java - page 509

String hostName = "www.darwinsys.com" ;
String ipNumber = "8.8.8.8" ; // currently a well-known Google DNS server

// Show getting the InetAddress (looking up a host) by host name
System . out . println ( hostName + "'s address is " +
InetAddress . getByName ( hostName ). getHostAddress ());

// Look up a host by address
System . out . println ( ipNumber + "'s name is " +
InetAddress . getByName ( ipNumber ). getHostName ());

// Look up my localhost addresss
final

final InetAddress localHost = InetAddress . getLocalHost ();
System . out . println ( "My localhost address is " + localHost );

// Show getting the InetAddress from an open Socket
String someServerName = "www.google.com" ;
// assuming there's a web server on the named server:
Socket theSocket = new new Socket ( someServerName , 80 );

InetAddress remote = theSocket . getInetAddress ();
System . out . printf ( "The InetAddress for %s is %s%n" ,
someServerName , remote );

}

}

You can also get an InetAddress from a Socket by calling its getInetAddress() method.
You can construct a Socket using an InetAddress instead of a hostname string. So, to con-
nect to port number myPortNumber on the same host as an existing socket, you'd use:

InetAddress remote = theSocket.getInetAddress( );
Socket anotherSocket = new Socket(remote, myPortNumber);

Finally, to look up all the addresses associated with a host—a server may be on more than
one network—use the static method getAllByName(host) , which returns an array of
InetAddress objects, one for each IP address associated with the given name.

A static method getLocalHost() returns an InetAddress equivalent to “localhost” or
127.0.0.1. This can be used to connect to a server program running on the same machine as
the client.

If you are using IPv6, you can use Inet6Address instead.