This exception signals that a socket cannot be connected to a remote host because the host cannot be contacted. Typically, this means that some link in the network between the local machine and the remote host is down or that the host is behind a firewall.

Figure 12-14. java.net.NoRouteToHostException

public class NoRouteToHostException extends SocketException {
// Public Constructors
     public NoRouteToHostException( );  
     public NoRouteToHostException(String msg);  
}