Whois improvements

app/src/main/java/eu/faircode/email/FragmentDialogOpenLink.java

@@ -461,7 +461,7 @@ public class FragmentDialogOpenLink extends FragmentDialogBase {
                         ibInfo.setOnClickListener(new View.OnClickListener() {
                             @Override
                             public void onClick(View v) {
-                                Uri uri = Uri.parse("https://en.wikipedia.org/wiki/WHOIS");
+                                Uri uri = Uri.parse(Whois.WHOIS_INFO);
                                 Helper.view(v.getContext(), uri, true);
                             }
                         });

app/src/main/java/eu/faircode/email/Whois.java

@@ -23,11 +23,15 @@ import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.net.Socket;
 import java.net.UnknownHostException;
+import java.nio.charset.StandardCharsets;
 
 public class Whois {
-    // https://datatracker.ietf.org/doc/html/rfc812
+    // https://datatracker.ietf.org/doc/html/rfc3912
+    static final String WHOIS_INFO = "https://en.wikipedia.org/wiki/WHOIS";
     private static final int WHOIS_PORT = 43;
     private static final int WHOIS_TIMEOUT = 15 * 1000; // milliseconds
+    private static final String WHOIS_IANA = "whois.iana.org";
+    private static final String WHOIS_PREFIX = "whois:";
 
     static String get(String domain) throws IOException {
         return get(domain, getServer(domain), WHOIS_PORT);
@@ -41,19 +45,21 @@ public class Whois {
         Socket socket = new Socket();
         socket.connect(new InetSocketAddress(host, port), WHOIS_TIMEOUT);
         try {
-            socket.getOutputStream().write((domain + "\r\n").getBytes());
-            return host + ":" + port + "\n" + Helper.readStream(socket.getInputStream());
+            byte[] request = (domain + "\r\n").getBytes(StandardCharsets.ISO_8859_1);
+            socket.getOutputStream().write(request);
+            String response = Helper.readStream(socket.getInputStream(), StandardCharsets.ISO_8859_1);
+            return host + ":" + port + "\n" + response;
         } finally {
             socket.close();
         }
     }
 
     private static String getServer(String domain) throws IOException {
-        String who = get(domain, "whois.iana.org");
-        for (String w : who.split("\\r?\\n"))
-            if (w.startsWith("whois:"))
-                return w.substring(6).trim();
-        Log.w(who);
+        String iana = get(domain, WHOIS_IANA);
+        for (String line : iana.split("\\r?\\n"))
+            if (line.startsWith(WHOIS_PREFIX))
+                return line.substring(WHOIS_PREFIX.length()).trim();
+        Log.w(iana);
         throw new UnknownHostException("whois server unknown " + domain);
     }
 }