Initial check-in.

git-svn-id: http://svn.igniterealtime.org/svn/repos/messenger/trunk@1347 b35dd754-fafc-0310-a699-88a17e54d16e

src/java/org/jivesoftware/messenger/net/DNSUtil.java

+/**
+ * $RCSfile$
+ * $Revision$
+ * $Date$
+ *
+ * Copyright (C) 2004-2005 Jive Software. All rights reserved.
+ *
+ * This software is published under the terms of the GNU Public License (GPL),
+ * a copy of which is included in this distribution.
+ */
+
+package org.jivesoftware.messenger.net;
+
+import org.jivesoftware.util.Log;
+
+import javax.naming.directory.Attributes;
+import javax.naming.directory.InitialDirContext;
+import javax.naming.directory.DirContext;
+import java.util.Hashtable;
+
+/**
+ * Utilty class to perform DNS lookups for XMPP services.
+ *
+ * @author Matt Tucker
+ */
+public class DNSUtil {
+
+    private static DirContext context;
+
+    static {
+        try {
+            Hashtable env = new Hashtable();
+            env.put("java.naming.factory.initial", "com.sun.jndi.dns.DnsContextFactory");
+            context = new InitialDirContext(env);
+        }
+        catch (Exception e) {
+            Log.error(e);
+        }
+    }
+
+    /**
+     * Returns the host name and port that the specified XMPP server can be
+     * reached at for server-to-server communication. A DNS lookup for a SRV
+     * record in the form "_xmpp-server._tcp.example.com" is attempted, according
+     * to section 14.4 of RFC 3920. If that lookup fails, a lookup in the older form
+     * of "_jabber._tcp.example.com" is attempted since servers that implement an
+     * older version of the protocol may be listed using that notation. If that
+     * lookup fails as well, it's assumed that the XMPP server lives at the
+     * host resolved by a DNS lookup at the specified domain on the default port
+     * of 5269.<p>
+     *
+     * As an example, a lookup for "example.com" may return "im.example.com:5269".
+     *
+     * @param domain the domain.
+     * @return a HostAddress, which encompasses the hostname and port that the XMPP
+     *      server can be reached at for the specified domain.
+     */
+    public static HostAddress resolveXMPPServerDomain(String domain) {
+        if (context == null) {
+            return new HostAddress(domain, 5269);
+        }
+        String host = domain;
+        int port = 5269;
+        try {
+            Attributes dnsLookup = context.getAttributes("_xmpp-server._tcp." + domain);
+            String srvRecord = (String)dnsLookup.get("SRV").get();
+            String [] srvRecordEntries = srvRecord.split(" ");
+            port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
+            host = srvRecordEntries[srvRecordEntries.length-1];
+        }
+        catch (Exception e) {
+            // Attempt lookup with older "jabber" name.
+            try {
+                Attributes dnsLookup = context.getAttributes("_jabber._tcp." + domain);
+                String srvRecord = (String)dnsLookup.get("SRV").get();
+                String [] srvRecordEntries = srvRecord.split(" ");
+                port = Integer.parseInt(srvRecordEntries[srvRecordEntries.length-2]);
+                host = srvRecordEntries[srvRecordEntries.length-1];
+            }
+            catch (Exception e2) { }
+        }
+        // Host entries in DNS should end with a ".".
+        if (host.endsWith(".")) {
+            host = host.substring(0, host.length()-1);
+        }
+        return new HostAddress(domain, port);
+    }
+
+    /**
+     * Encapsulates a hostname and port.
+     */
+    public static class HostAddress {
+
+        private String host;
+        private int port;
+
+        private HostAddress(String host, int port) {
+            this.host = host;
+            this.port = port;
+        }
+
+        /**
+         * Returns the hostname.
+         *
+         * @return the hostname.
+         */
+        public String getHost() {
+            return host;
+        }
+
+        /**
+         * Returns the port.
+         *
+         * @return the port.
+         */
+        public int getPort() {
+            return port;
+        }
+
+        public String toString() {
+            return host + ":" + port;
+        }
+    }
+}
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