Initial commit

Java/Messenger/.idea/.gitignore

@@ -0,0 +1,3 @@
+# Default ignored files
+/shelf/
+/workspace.xml

Java/Messenger/.idea/compiler.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CompilerConfiguration">
+    <annotationProcessing>
+      <profile name="Maven default annotation processors profile" enabled="true">
+        <sourceOutputDir name="target/generated-sources/annotations" />
+        <sourceTestOutputDir name="target/generated-test-sources/test-annotations" />
+        <outputRelativeToContentRoot value="true" />
+        <module name="Messenger" />
+      </profile>
+    </annotationProcessing>
+  </component>
+</project>

Java/Messenger/.idea/discord.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="DiscordProjectSettings">
+    <option name="show" value="PROJECT_FILES" />
+  </component>
+</project>

Java/Messenger/.idea/jarRepositories.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="RemoteRepositoriesConfiguration">
+    <remote-repository>
+      <option name="id" value="central" />
+      <option name="name" value="Central Repository" />
+      <option name="url" value="https://repo.maven.apache.org/maven2" />
+    </remote-repository>
+    <remote-repository>
+      <option name="id" value="central" />
+      <option name="name" value="Maven Central repository" />
+      <option name="url" value="https://repo1.maven.org/maven2" />
+    </remote-repository>
+    <remote-repository>
+      <option name="id" value="jboss.community" />
+      <option name="name" value="JBoss Community repository" />
+      <option name="url" value="https://repository.jboss.org/nexus/content/repositories/public/" />
+    </remote-repository>
+  </component>
+</project>

Java/Messenger/.idea/misc.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="MavenProjectsManager">
+    <option name="originalFiles">
+      <list>
+        <option value="$PROJECT_DIR$/pom.xml" />
+      </list>
+    </option>
+  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" default="true" project-jdk-name="11" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

Java/Messenger/.idea/uiDesigner.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Palette2">
+    <group name="Swing">
+      <item class="com.intellij.uiDesigner.HSpacer" tooltip-text="Horizontal Spacer" icon="/com/intellij/uiDesigner/icons/hspacer.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="1" hsize-policy="6" anchor="0" fill="1" />
+      </item>
+      <item class="com.intellij.uiDesigner.VSpacer" tooltip-text="Vertical Spacer" icon="/com/intellij/uiDesigner/icons/vspacer.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="1" anchor="0" fill="2" />
+      </item>
+      <item class="javax.swing.JPanel" icon="/com/intellij/uiDesigner/icons/panel.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="3" hsize-policy="3" anchor="0" fill="3" />
+      </item>
+      <item class="javax.swing.JScrollPane" icon="/com/intellij/uiDesigner/icons/scrollPane.png" removable="false" auto-create-binding="false" can-attach-label="true">
+        <default-constraints vsize-policy="7" hsize-policy="7" anchor="0" fill="3" />
+      </item>
+      <item class="javax.swing.JButton" icon="/com/intellij/uiDesigner/icons/button.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="3" anchor="0" fill="1" />
+        <initial-values>
+          <property name="text" value="Button" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JRadioButton" icon="/com/intellij/uiDesigner/icons/radioButton.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="3" anchor="8" fill="0" />
+        <initial-values>
+          <property name="text" value="RadioButton" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JCheckBox" icon="/com/intellij/uiDesigner/icons/checkBox.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="3" anchor="8" fill="0" />
+        <initial-values>
+          <property name="text" value="CheckBox" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JLabel" icon="/com/intellij/uiDesigner/icons/label.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="0" anchor="8" fill="0" />
+        <initial-values>
+          <property name="text" value="Label" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JTextField" icon="/com/intellij/uiDesigner/icons/textField.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1">
+          <preferred-size width="150" height="-1" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JPasswordField" icon="/com/intellij/uiDesigner/icons/passwordField.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1">
+          <preferred-size width="150" height="-1" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JFormattedTextField" icon="/com/intellij/uiDesigner/icons/formattedTextField.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1">
+          <preferred-size width="150" height="-1" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTextArea" icon="/com/intellij/uiDesigner/icons/textArea.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTextPane" icon="/com/intellij/uiDesigner/icons/textPane.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JEditorPane" icon="/com/intellij/uiDesigner/icons/editorPane.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JComboBox" icon="/com/intellij/uiDesigner/icons/comboBox.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="2" anchor="8" fill="1" />
+      </item>
+      <item class="javax.swing.JTable" icon="/com/intellij/uiDesigner/icons/table.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JList" icon="/com/intellij/uiDesigner/icons/list.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="2" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTree" icon="/com/intellij/uiDesigner/icons/tree.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTabbedPane" icon="/com/intellij/uiDesigner/icons/tabbedPane.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="3" hsize-policy="3" anchor="0" fill="3">
+          <preferred-size width="200" height="200" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JSplitPane" icon="/com/intellij/uiDesigner/icons/splitPane.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="3" hsize-policy="3" anchor="0" fill="3">
+          <preferred-size width="200" height="200" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JSpinner" icon="/com/intellij/uiDesigner/icons/spinner.png" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1" />
+      </item>
+      <item class="javax.swing.JSlider" icon="/com/intellij/uiDesigner/icons/slider.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1" />
+      </item>
+      <item class="javax.swing.JSeparator" icon="/com/intellij/uiDesigner/icons/separator.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3" />
+      </item>
+      <item class="javax.swing.JProgressBar" icon="/com/intellij/uiDesigner/icons/progressbar.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="0" fill="1" />
+      </item>
+      <item class="javax.swing.JToolBar" icon="/com/intellij/uiDesigner/icons/toolbar.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="0" fill="1">
+          <preferred-size width="-1" height="20" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JToolBar$Separator" icon="/com/intellij/uiDesigner/icons/toolbarSeparator.png" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="0" anchor="0" fill="1" />
+      </item>
+      <item class="javax.swing.JScrollBar" icon="/com/intellij/uiDesigner/icons/scrollbar.png" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="0" anchor="0" fill="2" />
+      </item>
+    </group>
+  </component>
+</project>

Java/Messenger/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>de.craftix</groupId>
+    <artifactId>Messenger</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>11</maven.compiler.source>
+        <maven.compiler.target>11</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
+        <dependency>
+            <groupId>mysql</groupId>
+            <artifactId>mysql-connector-java</artifactId>
+            <version>8.0.26</version>
+        </dependency>
+
+        <dependency>
+            <groupId>de.craftix</groupId>
+            <artifactId>GameEngine</artifactId>
+            <version>3.0</version>
+            <scope>system</scope>
+            <systemPath>D:/Java/GameEngine/target/GameEngine-3.0.jar</systemPath>
+        </dependency>
+    </dependencies>
+
+</project>

Java/Messenger/src/main/java/de/craftix/messenger/Messenger.java

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+package de.craftix.messenger;
+
+import de.craftix.engine.GameEngine;
+import de.craftix.engine.render.Screen;
+import de.craftix.messenger.onscreen.ComponentManager;
+import de.craftix.server.User;
+
+import java.util.Base64;
+
+public class Messenger extends GameEngine {
+    private static User user;
+
+    public static void main(String[] args) {
+        Screen.antialiasing(true);
+        Screen.showFrames(true);
+        Screen.setResizeable(true);
+        Screen.setFramesPerSecond(120);
+        Screen.setAntialiasingEffectTextures(false);
+        setup(800, 600, "Messenger v0.1", new Messenger(), 20);
+
+        //ServerConnection.connect();
+    }
+
+    @Override
+    public void initialise() {
+        ComponentManager.setup();
+    }
+
+    public static User getUser() { return user; }
+
+    public static String decode(String msg) {
+        return new String(Base64.getDecoder().decode(msg));
+    }
+    public static String encode(String msg) {
+        return Base64.getEncoder().encodeToString(msg.getBytes());
+    }
+}

Java/Messenger/src/main/java/de/craftix/messenger/ServerConnection.java

@@ -0,0 +1,91 @@
+package de.craftix.messenger;
+
+import de.craftix.server.Packet;
+import de.craftix.server.Server;
+import sun.misc.Unsafe;
+
+import java.io.BufferedInputStream;
+import java.io.BufferedOutputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+
+public class ServerConnection {
+
+    private static ObjectInputStream in;
+    private static ObjectOutputStream out;
+    private static Thread clientThread;
+
+    public static void connect() {
+        try {
+            Socket socket = new Socket();
+            socket.connect(new InetSocketAddress(Server.IP, Server.PORT), 5000);
+            out = new ObjectOutputStream(new BufferedOutputStream(socket.getOutputStream()));
+            out.flush();
+            in = new ObjectInputStream(new BufferedInputStream(socket.getInputStream()));
+
+            disableWarning();
+
+            System.out.println("Connected to Server");
+
+            startThread();
+        }catch (Exception e) { e.printStackTrace(); }
+    }
+
+    private static void startThread() {
+        clientThread = new Thread(() -> {
+            while (!clientThread.isInterrupted()) {
+                try {
+                    Object o = in.readObject();
+                    if (o instanceof Packet) {
+                        Packet packet = (Packet) o;
+                        Packet output = handlePacket(packet);
+                        out.writeObject(output);
+                        out.flush();
+                    }
+                }catch (Exception e) { e.printStackTrace(); }
+            }
+        });
+        clientThread.start();
+    }
+
+    private static Packet handlePacket(Packet packet) {
+        if (packet.getType() == Packet.PacketType.PING)
+            return new Packet(Packet.PacketType.PING, null);
+
+        return new Packet(Packet.PacketType.BOOLEAN, false);
+    }
+
+    public static Packet sendRequest(Packet packet) {
+        Packet answer = new Packet(Packet.PacketType.BOOLEAN, false);
+        try {
+            //Kill Thread
+            Method m = Thread.class.getDeclaredMethod("stop0", Object.class);
+            m.setAccessible(true);
+            m.invoke(clientThread, new ThreadDeath());
+
+            out.writeObject(packet);
+            out.flush();
+            Object o = in.readObject();
+            if (o instanceof Packet)
+                answer = (Packet) o;
+        }catch (Exception e) { e.printStackTrace(); }
+        finally { startThread(); }
+        return answer;
+    }
+
+    private static void disableWarning() {
+        try {
+            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
+            theUnsafe.setAccessible(true);
+            Unsafe u = (Unsafe) theUnsafe.get(null);
+
+            Class<?> cls = Class.forName("jdk.internal.module.IllegalAccessLogger");
+            Field logger = cls.getDeclaredField("logger");
+            u.putObjectVolatile(cls, u.staticFieldOffset(logger), null);
+        } catch (Exception ignored) {}
+    }
+}

Java/Messenger/src/main/java/de/craftix/messenger/onscreen/ComponentManager.java

@@ -0,0 +1,21 @@
+package de.craftix.messenger.onscreen;
+
+import de.craftix.engine.render.Sprite;
+import de.craftix.engine.var.*;
+import de.craftix.messenger.Messenger;
+
+import java.awt.Image;
+import java.awt.image.BufferedImage;
+
+public class ComponentManager {
+    private final static Scene mainScene = new Scene();
+
+    public static void setup() {
+        mainScene.setBackground(new Sprite(new BufferedImage(800, 600, Image.SCALE_DEFAULT), false), false);
+
+        // TODO: Add Components
+
+        Messenger.setActiveScene(mainScene);
+    }
+
+}

Java/Messenger/src/main/java/de/craftix/server/ClientHandler.java

@@ -0,0 +1,95 @@
+package de.craftix.server;
+
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.net.Socket;
+
+public class ClientHandler {
+    protected String address;
+    protected Socket con;
+    protected ObjectInputStream in;
+    protected ObjectOutputStream out;
+    protected Thread clientThread;
+    protected User user;
+
+    protected ClientHandler(Socket con, ObjectInputStream in, ObjectOutputStream out) {
+        this.con = con;
+        this.in = in;
+        this.out = out;
+        this.address = con.getInetAddress().getHostAddress() + ":" + con.getPort();
+
+        System.out.println("Client connected [" + address + "]");
+
+        startClientThread();
+    }
+
+    private void startClientThread() {
+        clientThread = new Thread(() -> {
+            while (!clientThread.isInterrupted()) {
+                try {
+                    Object o = in.readObject();
+                    if (o instanceof Packet) {
+                        Packet output = handlePacket((Packet) o);
+                        sendPacket(output);
+                    }
+                }catch (Exception e) {
+                    disconnect();
+                }
+            }
+        });
+        clientThread.start();
+    }
+
+    private void disconnect() {
+        clientThread.interrupt();
+        Server.clients.remove(this);
+
+        System.out.println("Client disconnected [" + address + "]");
+    }
+
+    public void sendPacket(Packet packet) {
+        try {
+            out.writeObject(packet);
+            out.flush();
+        }catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    private Packet handlePacket(Packet packet) {
+        if (packet.getType() == Packet.PacketType.PING)
+            return new Packet(Packet.PacketType.PING, null);
+
+        if (packet.getType() == Packet.PacketType.LOGIN) {
+            String[] arr = (String[]) packet.getValue();
+            String username = arr[0];
+            String password = arr[1];
+            User user = User.getUser(username);
+            assert user != null;
+            if (Server.checkPassword(user.getUniqueID(), password)) {
+                this.user = user;
+                return new Packet(Packet.PacketType.GET_USER, user);
+            }
+            else
+                return new Packet(Packet.PacketType.BOOLEAN, false);
+        }
+
+        if (packet.getType() == Packet.PacketType.REGISTER) {
+            String[] arr = (String[]) packet.getValue();
+            String username = arr[0];
+            String password = arr[1];
+            User[] users = User.getUsers();
+            for (User u : users) {
+                if (u.username.equals(username))
+                    return new Packet(Packet.PacketType.BOOLEAN, false);
+            }
+            User.createUser(User.Rank.USER, username, password);
+            User user = User.getUser(username);
+            this.user = user;
+            return new Packet(Packet.PacketType.GET_USER, user);
+        }
+
+        return new Packet(Packet.PacketType.BOOLEAN, false);
+    }
+
+}

Java/Messenger/src/main/java/de/craftix/server/MySQL.java

@@ -0,0 +1,61 @@
+package de.craftix.server;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+
+public class MySQL {
+
+    protected static String server;
+    protected static int port;
+    protected static String database;
+    protected static String username;
+    protected static String password;
+    protected static Connection con;
+
+    public static void connect() {
+        if (isConnected()) return;
+        try {
+            Class.forName("com.mysql.cj.jdbc.Driver");
+            con = DriverManager.getConnection("jdbc:mysql://" + server + ":" + port + "/" + database, username, password);
+        }catch (Exception e) {
+            e.printStackTrace();
+        }
+        System.out.println("MySQL connected");
+    }
+
+    public static void disconnect() {
+        if (!isConnected()) return;
+        try {
+            con.close();
+            con = null;
+        }catch (Exception e) {
+            e.printStackTrace();
+        }
+        System.out.println("MySQL disconnected");
+    }
+
+    public static boolean isConnected() {
+        return con != null;
+    }
+
+    public static void insert(String qry) {
+        if (!isConnected()) throw new NullPointerException("MySQL not connected");
+        try {
+            con.prepareStatement(qry).executeUpdate();
+        }catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    public static ResultSet getData(String qry) {
+        if (!isConnected()) throw new NullPointerException("MySQL not connected");
+        try {
+            return con.prepareStatement(qry).executeQuery();
+        }catch (Exception e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+}

Java/Messenger/src/main/java/de/craftix/server/Packet.java

@@ -0,0 +1,43 @@
+package de.craftix.server;
+
+import java.io.Serializable;
+
+public class Packet implements Serializable {
+
+    public enum PacketType {
+        PING(0),
+        UPDATE(1),
+        GET_USER(2),
+        LOGIN(3),
+        REGISTER(4),
+        BOOLEAN(5);
+
+        private final byte id;
+        PacketType(int id)
+        { this.id = (byte) id; }
+
+        public byte getID()
+        { return id; }
+
+        public static PacketType getByID(byte id) {
+            for (PacketType type : values()) {
+                if (type.getID() == id)
+                    return type;
+            }
+            return PING;
+        }
+    }
+
+    private final Object value;
+    private final byte type;
+
+    public Packet(PacketType type, Object value) {
+        this.value = value;
+        this.type = type.getID();
+    }
+
+    public PacketType getType()
+    { return PacketType.getByID(type); }
+    public Object getValue()
+    { return value; }
+}

Java/Messenger/src/main/java/de/craftix/server/Server.java

@@ -0,0 +1,64 @@
+package de.craftix.server;
+
+import java.io.*;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.sql.ResultSet;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+
+public class Server {
+    public static final String IP = "localhost";
+    public static final int PORT = 187;
+
+    protected static ServerSocket socket;
+    protected static List<ClientHandler> clients;
+
+    public static void main(String[] args) throws Exception {
+        MySQL.server = "213.136.89.237";
+        MySQL.port = 3306;
+        MySQL.database = "Messenger";
+        MySQL.username = "Messenger";
+        MySQL.password = "v0dn2Ml60AcaX@VN";
+
+        MySQL.connect();
+        createMySQLTables();
+
+        startServerLoop();
+    }
+
+    private static void createMySQLTables() {
+        MySQL.insert("CREATE TABLE IF NOT EXISTS Users (Rank INT(10), ID INT(10), UUID VARCHAR(100), Username VARCHAR(100), Password VARCHAR(100))");
+        MySQL.insert("CREATE TABLE IF NOT EXISTS Chats (ID INT(10), Owner VARCHAR(100))");
+        MySQL.insert("CREATE TABLE IF NOT EXISTS ChatUser (ChatID INT(10), Member VARCHAR(100))");
+        MySQL.insert("CREATE TABLE IF NOT EXISTS Messages (Chat INT(10), Sender VARCHAR(100), Timestamp INT(255), Message VARCHAR(2000))");
+    }
+
+    private static void startServerLoop() throws Exception {
+        socket = new ServerSocket(PORT);
+        clients = new ArrayList<>();
+
+        System.out.println("Server started successfully");
+
+        while (!Thread.currentThread().isInterrupted()) {
+            Socket client = socket.accept();
+            ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(client.getOutputStream()));
+            out.flush();
+            ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(client.getInputStream()));
+            clients.add(new ClientHandler(client, in, out));
+        }
+    }
+
+    protected static boolean checkPassword(UUID user, String password) {
+        try {
+            ResultSet rs = MySQL.getData("SELECT Password FROM Users WHERE UUID = \"" + user + "\"");
+            assert rs != null;
+            if (rs.next()) {
+                String truePassword = rs.getString("Password");
+                return password.equals(truePassword);
+            }
+        }catch (Exception e) { e.printStackTrace(); }
+        return false;
+    }
+}

Java/Messenger/src/main/java/de/craftix/server/User.java

@@ -0,0 +1,130 @@
+package de.craftix.server;
+
+import java.io.Serializable;
+import java.sql.ResultSet;
+import java.util.ArrayList;
+import java.util.UUID;
+
+public class User implements Serializable {
+    public static User getUser(UUID uuid) {
+        if (!MySQL.isConnected()) throw new NullPointerException("MySQL not connected!");
+        try {
+            ResultSet rs = MySQL.getData("SELECT * FROM Users WHERE UUID = \"" + uuid + "\"");
+            assert rs != null;
+            if (rs.next()) {
+                int id = rs.getInt("ID");
+                Rank rank = Rank.getRankByID(rs.getInt("Rank"));
+                String username = rs.getString("Username");
+                return new User(id, uuid, rank, username);
+            }
+        }catch (Exception e) { e.printStackTrace(); }
+        return null;
+    }
+    public static User getUser(String username) {
+        if (!MySQL.isConnected()) throw new NullPointerException("MySQL not connected!");
+        try {
+            ResultSet rs = MySQL.getData("SELECT * FROM Users WHERE Username = \"" + username + "\"");
+            assert rs != null;
+            if (rs.next()) {
+                int id = rs.getInt("ID");
+                UUID uuid = UUID.fromString(rs.getString("UUID"));
+                Rank rank = Rank.getRankByID(rs.getInt("Rank"));
+                return new User(id, uuid, rank, username);
+            }
+        }catch (Exception e) { e.printStackTrace(); }
+        return null;
+    }
+    public static User[] getUsers() {
+        if (!MySQL.isConnected()) throw new NullPointerException("MySQL not connected!");
+        ArrayList<User> users = new ArrayList<>();
+
+        try {
+            ResultSet rs = MySQL.getData("SELECT * FROM Users");
+            assert rs != null;
+            if (rs.next()) {
+                int id = rs.getInt("ID");
+                UUID uuid = UUID.fromString(rs.getString("UUID"));
+                Rank rank = Rank.getRankByID(rs.getInt("Rank"));
+                String username = rs.getString("Username");
+                users.add(new User(id, uuid, rank, username));
+            }
+        }catch (Exception e) { e.printStackTrace(); }
+
+        return users.toArray(new User[0]);
+    }
+
+    protected static User createUser(Rank rank, String username, String password) {
+        User[] users = getUsers();
+
+        int id = 0;
+        boolean foundID = false;
+        while (!foundID) {
+            for (User u : users) {
+                if (u.id == id) {
+                    id++;
+                    break;
+                }
+            }
+            foundID = true;
+        }
+
+        UUID uuid = UUID.randomUUID();
+        boolean foundUUID = false;
+        while (!foundUUID) {
+            for (User u : users) {
+                if (u.uuid.equals(uuid)) {
+                    uuid = UUID.randomUUID();
+                    break;
+                }
+            }
+            foundUUID = true;
+        }
+
+        User user = new User(id, uuid, rank, username);
+        MySQL.insert("INSERT INTO Users (Rank, ID, UUID, Username, Password) VALUES (" + rank.getRankID() + ", " + id + ", \"" + uuid + "\", \"" +
+                                                                                         username + "\", \"" + password + "\")");
+
+        return user;
+    }
+
+    private final int id;
+    private final UUID uuid;
+    protected Rank rank;
+    protected String username;
+
+    private User(int id, UUID uuid, Rank rank, String username) {
+        this.id = id;
+        this.uuid = uuid;
+        this.rank = rank;
+        this.username = username;
+    }
+
+    protected void saveUser() {
+        if (!MySQL.isConnected()) throw new NullPointerException("MySQL not connected!");
+        MySQL.insert("UPDATE Users SET Username = \"" + username + "\", Rank = " + rank + " WHERE UUID = \"" + uuid + "\"");
+    }
+
+    public int getID() { return id; }
+    public UUID getUniqueID() { return uuid; }
+    public Rank getRank() { return rank; }
+    public String getUsername() { return username; }
+
+    public enum Rank implements Serializable {
+        USER(0),
+        PREMIUM(1),
+        MODERATOR(2),
+        ADMINISTRATOR(3);
+
+        private final int rankID;
+        Rank(int rank) { this.rankID = rank; }
+        public int getRankID() { return rankID; }
+
+        public static Rank getRankByID(int id) {
+            for (Rank rank : values()) {
+                if (rank.getRankID() == id)
+                    return rank;
+            }
+            return null;
+        }
+    }
+}