3030import java .io .IOException ;
3131import java .io .InputStreamReader ;
3232import java .net .HttpURLConnection ;
33+ import java .net .InetSocketAddress ;
3334import java .net .URISyntaxException ;
3435import java .net .URL ;
36+ import java .util .regex .Pattern ;
37+
38+ import org .spoutcraft .client .gui .server .ServerItem ;
39+ import org .xbill .DNS .Lookup ;
40+ import org .xbill .DNS .Record ;
41+ import org .xbill .DNS .SRVRecord ;
42+ import org .xbill .DNS .TextParseException ;
43+ import org .xbill .DNS .Type ;
3544
3645public class NetworkUtils {
46+ /**
47+ * A {@link Pattern} matching valid DNS hostnames (as opposed to IP addresses).
48+ */
49+ private static final Pattern HOSTNAME_PATTERN = Pattern .compile ("[a-zA-Z-]" );
50+
3751 public static void pingUrl (String Url ) {
3852 try {
3953 URL url = new URL (Url );
@@ -58,4 +72,96 @@ public static void openInBrowser(String url) {
5872 e .printStackTrace ();
5973 }
6074 }
75+
76+ /**
77+ * Resolves a hostname to an {@link InetSocketAddress}, encapsulating an IP address and
78+ * port. <code>hostname</code> may represent a valid DNS hostname or an IP address. If
79+ * <code>hostname</code> is a valid DNS hostname <em>and</em> <code>port</code> is equal
80+ * to {@link ServerItem#DEFAULT_PORT} (implying the user may not have specified a server
81+ * port), a <a href="http://en.wikipedia.org/wiki/SRV_record">SRV record</a> lookup may
82+ * be attempted—see {@link #resolve(String)} for implementation details.
83+ * <p>
84+ * This method is the equivalent of passing <code>true</code> to {@link #resolve(String, int, boolean)}.
85+ *
86+ * @param hostname the DNS hostname to resolve.
87+ * @param port the port number to encapsulate within the <code>InetSocketAddress</code>.
88+ * @return an {@link InetSocketAddress}, which may be marked unresolved if hostname lookup failed.
89+ */
90+ public static InetSocketAddress resolve (String hostname , int port ) {
91+ return resolve (hostname , port , true );
92+ }
93+
94+ /**
95+ * Resolves a hostname to an {@link InetSocketAddress}, encapsulating an IP address and
96+ * port. An optional <a href="http://en.wikipedia.org/wiki/SRV_record">SRV record</a>
97+ * lookup may be attempted—see {@link #resolve(String)} for implementation details.
98+ * A SRV record lookup will only be attempted if <code>hostname</code> represents a valid
99+ * DNS hostname, and <code>port</code> is equal to {@link ServerItem#DEFAULT_PORT} (implying
100+ * the user may not have specified a server port).
101+ * <p>
102+ * If <code>srv</code> is <code>true</code> and SRV record lookup fails or returns no
103+ * results, a regular DNS lookup will be attempted.
104+ * <p>
105+ * If the given <code>hostname</code> represents an IP address, it will not be resolved.
106+ *
107+ * @param hostname the DNS hostname to resolve.
108+ * @param port the port number to encapsulate within the <code>InetSocketAddress</code>.
109+ * @param srv whether to attempt a SRV record lookup.
110+ * @return an {@link InetSocketAddress}, which may be marked unresolved if hostname lookup failed.
111+ */
112+ public static InetSocketAddress resolve (String hostname , int port , boolean srv ) {
113+ if (srv && (port == ServerItem .DEFAULT_PORT ) && (HOSTNAME_PATTERN .matcher (hostname ).find ())) {
114+ try {
115+ InetSocketAddress address = resolve (hostname );
116+ if (address != null ) {
117+ return address ;
118+ }
119+ } catch (TextParseException e ) {
120+ // Do nothing: fall back on a regular DNS lookup before failing
121+ }
122+ }
123+
124+ return new InetSocketAddress (hostname , port );
125+ }
126+
127+ /**
128+ * Resolves a hostname to an {@link InetSocketAddress}, encapsulating an IP address and
129+ * port, using a <a href="http://en.wikipedia.org/wiki/SRV_record">SRV record</a> lookup.
130+ * This method assumes <code>minecraft</code> as the service name during the DNS query,
131+ * such that a matching record looks like:
132+ * <p>
133+ * <code>_minecraft._tcp.example.com. 86400 IN SRV 0 1 25565 minecraft.example.com.</code>
134+ * <p>
135+ * If multiple SRV records exist for a given hostname, the record with the highest priority
136+ * (that is, the lowest priority value) is selected. This implementation does not take
137+ * into account relative weights for records with identical priorities, and behavior in
138+ * such cases is undefined.
139+ *
140+ * @param hostname the DNS hostname to on which to perform a SRV lookup.
141+ * @return an {@link InetSocketAddress}, or <code>null</code> if no SRV record was found.
142+ * @throws TextParseException if the hostname is malformed.
143+ */
144+ public static InetSocketAddress resolve (String hostname ) throws TextParseException {
145+ String query = "_minecraft._tcp." + hostname .trim ();
146+ Record [] records = new Lookup (query , Type .SRV ).run ();
147+
148+ if ((records != null ) && (records .length > 0 )) {
149+ SRVRecord srv = (SRVRecord )records [0 ];
150+
151+ if (records .length > 1 ) {
152+ for (int i = 1 ; i < records .length ; i ++) {
153+ SRVRecord record = (SRVRecord )records [i ];
154+ if (record .getPriority () < srv .getPriority ()) {
155+ srv = record ;
156+ }
157+ }
158+ }
159+
160+ String host = srv .getTarget ().toString ().replaceAll ("\\ .+$" , "" );
161+ int port = srv .getPort ();
162+ return new InetSocketAddress (host , port );
163+ }
164+
165+ return null ;
166+ }
61167}
0 commit comments