Work in progress on the implementation of parallel DNS queries.

test/net/Host.java

@@ -0,0 +1,129 @@
+/*
+ * SIP Communicator, the OpenSource Java VoIP and Instant Messaging client.
+ *
+ * Distributable under LGPL license.
+ * See terms of license at gnu.org.
+ */
+package net;
+
+import java.net.*;
+import java.text.*;
+import java.util.*;
+
+import org.xbill.DNS.*;
+
+import net.java.sip.communicator.util.*;
+
+/**
+ * A simple DNS utility that works.
+ *
+ * @author Emil Ivov
+ */
+public class Host
+{
+    /**
+     * The <tt>Logger</tt> used by the <tt>Host</tt>
+     * class and its instances for logging output.
+     */
+    private static final Logger logger = Logger.getLogger(Host.class.getName());
+
+    /**
+     * Returns array of hosts from the SRV record of the specified domain.
+     * The records are ordered against the SRV record priority
+     * @param domain the name of the domain we'd like to resolve (_proto._tcp
+     * included).
+     * @return an array of InetSocketAddress containing records returned by the
+     * DNS server - address and port .
+     * @throws ParseException if <tt>domain</tt> is not a valid domain name.
+     */
+    public static InetSocketAddress[] getSRVRecords(String domain)
+        throws ParseException
+    {
+        Record[] records = null;
+        try
+        {
+            Lookup lookup = new Lookup(domain, Type.SRV);
+            records = lookup.run();
+        }
+        catch (TextParseException tpe)
+        {
+            logger.error("Failed to parse domain="+domain, tpe);
+            throw new ParseException(tpe.getMessage(), 0);
+        }
+        if (records == null)
+        {
+            return null;
+        }
+
+        String[][] pvhn = new String[records.length][4];
+        for (int i = 0; i < records.length; i++)
+        {
+            SRVRecord srvRecord = (SRVRecord) records[i];
+            pvhn[i][0] = "" + srvRecord.getPriority();
+            pvhn[i][1] = "" + srvRecord.getWeight();
+            pvhn[i][2] = "" + srvRecord.getPort();
+            pvhn[i][3] = srvRecord.getTarget().toString();
+            if (pvhn[i][3].endsWith("."))
+            {
+                pvhn[i][3] = pvhn[i][3].substring(0, pvhn[i][3].length() - 1);
+            }
+        }
+
+        /* sort the SRV RRs by RR value (lower is preferred) */
+        Arrays.sort(pvhn, new Comparator<String[]>()
+        {
+            public int compare(String array1[], String array2[])
+            {
+                return (Integer.parseInt(   array1[0])
+                        - Integer.parseInt( array2[0]));
+            }
+        });
+
+        /* put sorted host names in an array, get rid of any trailing '.' */
+        ArrayList<InetSocketAddress> sortedHostNames
+            = new ArrayList<InetSocketAddress>();
+        for (int i = 0; i < pvhn.length; i++)
+        {
+            try
+            {
+                sortedHostNames.add(new InetSocketAddress(
+                        Address.getByName(pvhn[i][3]),
+                        Integer.valueOf(pvhn[i][2])));
+            }
+            catch(UnknownHostException e)
+            {
+                logger.warn("Unknown host: " + pvhn[i][3], e);
+            }
+        }
+
+        if (logger.isTraceEnabled())
+        {
+            logger.trace("DNS SRV query for domain " + domain + " returned:");
+            for (int i = 0; i < sortedHostNames.size(); i++)
+            {
+                if (logger.isTraceEnabled())
+                    logger.trace(sortedHostNames.get(i));
+            }
+        }
+        return sortedHostNames.toArray(new InetSocketAddress[0]);
+    }
+
+    /**
+     * Queries DNS servers
+     *
+     * @param args args
+     *
+     * @throws Throwable if anything goes wrong
+     */
+    public static void main(String[] args) throws Throwable
+    {
+        InetSocketAddress[] addrs
+                            = getSRVRecords("_xmpp-client._tcp.emcho.com");
+
+        for (InetSocketAddress addr : addrs)
+        {
+            //System.out.println("addr=" + addr.getAddress().getHostName());
+        }
+    }
+
+}