Added whois client

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

@@ -0,0 +1,43 @@
+package eu.faircode.email;
+
+/*
+    This file is part of FairEmail.
+
+    FairEmail is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    FairEmail is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with FairEmail.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2018-2022 by Marcel Bokhorst (M66B)
+*/
+
+import java.io.IOException;
+import java.net.Socket;
+
+public class Whois {
+    private static final String WHOIS_HOST = "whois.internic.net";
+    private static final int WHOIS_PORT = 43;
+
+    static String get(String domain) throws IOException {
+        return get(domain, WHOIS_HOST, WHOIS_PORT);
+    }
+
+    static String get(String domain, String host) throws IOException {
+        return get(domain, host, WHOIS_PORT);
+    }
+
+    static String get(String domain, String host, int port) throws IOException {
+        try (Socket socket = new Socket(host, port)) {
+            socket.getOutputStream().write((domain + "\n").getBytes());
+            return Helper.readStream(socket.getInputStream());
+        }
+    }
+}