ServiceNames.java

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import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Hashtable;

/**
 *  Encapsulates lookup database for TCP and UDP service names.
 *  
 *  @author Administrator
 */
public class ServiceNames 
{
    private Hashtable<String,String> hash;
    
    /**
     *  Creates instance from text file containing description of services 
     *  where each line describes one service, and is of the form:<pre>
     * 
     *   service-name  port/protocol  [aliases ...]   [# comment]
     *  
     *  </pre>The format is compatible with Unix' <code>/etc/services</code>. 
     */
    ServiceNames( String filename )
    {
        this.hash = new Hashtable<String,String> ();

        try
        {
            InputStream is = null;
            
            /* Read first local file
             */
            try {
                is = new FileInputStream( filename );
                System.out.println( "\nWarning: Loading local services.txt..." );
            } catch ( FileNotFoundException e2 ) {
                /* ignored */
            }

            /* then fail back to resource from the JAR
             */
            if ( is == null ) {
                is = getClass().getResourceAsStream( filename );
            }

            if ( is == null ) {
                System.out.println( "\nWarning: Could not find services.txt..." );
                return;
            }

            BufferedReader in = new BufferedReader( new InputStreamReader( is ) );
            
            for( String line = in.readLine (); line != null; line = in.readLine () ) 
            {
                /* Split string into words, removing all leading, trailing 
                 * and superfluous (betwewn words) white-spaces
                 */
                String[] words = line.trim().split( "\\s{1,}" );

                /* Ignore comments
                 */
                if ( words.length < 2 || words[0].equals( "#" ) ) {
                    continue;
                }

                /* Format:  <name>    <port number>/<port type>
                 *          words[0]  words[2]
                 *
                 * Example: nimgtw  48003/udp
                 * Example: smtp    25/tcp
                 */
                hash.put( words[1], words[0] );
            }

            is.close ();
        }
        catch( FileNotFoundException e )
        {
            System.err.println(
                    "\nFile " + filename + " not found.\n" 
                    + e.toString () );
        }
        catch( IOException e )
        {
            System.err.println(
                    "\nThere was a problem reading the services file.\n" 
                    + e.toString () );
        }
    }
    
    /**
     *  Lookups name for <em>port/protocol</em> from hash table.
     *  E.g. Lookup "25/tcp" should return "smtp".
     *  
     *  @param protocol  protocol name, e.g. "udp" or "tcp"
     *  @param port      port number
     */
    public String lookup( String protocol, int port )
    {
        if ( hash == null ) {
            return null;
        }

        String value = hash.get( port + "/" + protocol );
        
        return value != null ? value.toLowerCase () : null;
    }
    
    /**
     *  Verifies exisatnce of the common port names
     */
    public boolean sanityCheck ()
    {
        if ( hash == null ) {
            return false;
        }

        boolean ok = "smtp".equalsIgnoreCase( lookup( "tcp", 25 ) )
                  || "http".equalsIgnoreCase( lookup( "tcp", 80 ) )
                  || "ssh".equalsIgnoreCase( lookup( "tcp", 22 ) )
                  || "ssh".equalsIgnoreCase( lookup( "udp", 22 ) );
        
        if ( ! ok ) {
            System.err.println( "ServiceNames: Sanity check failed." );
        }
        
        return ok;
    }
}