Added ability to kick players.

client/src/main/java/nl/andrewl/aos2_client/Client.java

@@ -93,7 +93,7 @@ public class Client implements Runnable {
 		playerSource = new SoundSource();
 
 		long lastFrameAt = System.currentTimeMillis();
-		while (!gameRenderer.windowShouldClose()) {
+		while (!gameRenderer.windowShouldClose() && !communicationHandler.isDone()) {
 			long now = System.currentTimeMillis();
 			float dt = (now - lastFrameAt) / 1000f;
 			world.processQueuedChunkUpdates();

client/src/main/java/nl/andrewl/aos2_client/CommunicationHandler.java

@@ -39,6 +39,7 @@ public class CommunicationHandler {
 	private ExtendedDataOutputStream out;
 	private ExtendedDataInputStream in;
 	private int clientId;
+	private boolean done;
 
 	public CommunicationHandler(Client client) {
 		this.client = client;
@@ -71,7 +72,7 @@ public class CommunicationHandler {
 			log.debug("Initial data received.");
 			establishDatagramConnection();
 			log.info("Connection to server established. My client id is {}.", clientId);
-			new Thread(new TcpReceiver(in, client::onMessageReceived)).start();
+			new Thread(new TcpReceiver(in, client::onMessageReceived).withShutdownHook(this::shutdown)).start();
 			new Thread(new UdpReceiver(datagramSocket, (msg, packet) -> client.onMessageReceived(msg))).start();
 		} else {
 			throw new IOException("Server returned an unexpected message: " + response);
@@ -84,9 +85,15 @@ public class CommunicationHandler {
 			datagramSocket.close();
 		} catch (IOException e) {
 			e.printStackTrace();
+		} finally {
+			done = true;
 		}
 	}
 
+	public boolean isDone() {
+		return done;
+	}
+
 	public void sendMessage(Message msg) {
 		try {
 			Net.write(msg, out);

core/src/main/java/nl/andrewl/aos_core/UsernameChecker.java

@@ -0,0 +1,14 @@
+package nl.andrewl.aos_core;
+
+import java.util.regex.Pattern;
+
+public class UsernameChecker {
+	private static final int MIN_LENGTH = 3;
+	private static final int MAX_LENGTH = 24;
+	private static final Pattern pattern = Pattern.compile("[a-zA-Z]+[a-zA-Z\\d-_]*");
+
+	public static boolean isValid(String username) {
+		if (username.length() < MIN_LENGTH || username.length() > MAX_LENGTH) return false;
+		return pattern.matcher(username).matches();
+	}
+}

core/src/main/java/nl/andrewl/aos_core/net/UdpReceiver.java

@@ -18,10 +18,16 @@ public class UdpReceiver implements Runnable {
 
 	private final DatagramSocket socket;
 	private final UdpMessageHandler handler;
+	private final Runnable shutdownHook;
 
 	public UdpReceiver(DatagramSocket socket, UdpMessageHandler handler) {
+		this(socket, handler, null);
+	}
+
+	public UdpReceiver(DatagramSocket socket, UdpMessageHandler handler, Runnable shutdownHook) {
 		this.socket = socket;
 		this.handler = handler;
+		this.shutdownHook = shutdownHook;
 	}
 
 	@Override
@@ -39,12 +45,11 @@ public class UdpReceiver implements Runnable {
 				}
 				e.printStackTrace();
 			} catch (EOFException e) {
-				System.out.println("EOF!");
 				break;
 			} catch (IOException e) {
 				e.printStackTrace();
 			}
 		}
-		System.out.println("UDP receiver shut down.");
+		if (shutdownHook != null) shutdownHook.run();
 	}
 }

server/pom.xml

@@ -22,6 +22,17 @@
             <artifactId>aos2-core</artifactId>
             <version>${parent.version}</version>
         </dependency>
+        <dependency>
+            <groupId>info.picocli</groupId>
+            <artifactId>picocli-shell-jline3</artifactId>
+            <version>4.6.3</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/org.fusesource.jansi/jansi -->
+        <dependency>
+            <groupId>org.fusesource.jansi</groupId>
+            <artifactId>jansi</artifactId>
+            <version>2.4.0</version>
+        </dependency>
     </dependencies>
 
     <build>

server/src/main/java/nl/andrewl/aos2_server/ClientCommunicationHandler.java

@@ -2,6 +2,7 @@ package nl.andrewl.aos2_server;
 
 import nl.andrewl.aos2_server.model.ServerPlayer;
 import nl.andrewl.aos_core.Net;
+import nl.andrewl.aos_core.UsernameChecker;
 import nl.andrewl.aos_core.model.item.ItemStack;
 import nl.andrewl.aos_core.model.world.Chunk;
 import nl.andrewl.aos_core.model.world.WorldIO;
@@ -91,6 +92,18 @@ public class ClientCommunicationHandler {
 				Message msg = Net.read(in);
 				if (msg instanceof ConnectRequestMessage connectMsg) {
 					log.debug("Received connect request from player \"{}\"", connectMsg.username());
+					// Ensure the connection is valid.
+					if (!UsernameChecker.isValid(connectMsg.username())) {
+						Net.write(new ConnectRejectMessage("Invalid username."), out);
+						socket.close();
+						return;
+					}
+					if (server.getPlayerManager().getPlayers().stream().anyMatch(p -> p.getUsername().equals(connectMsg.username()))) {
+						Net.write(new ConnectRejectMessage("Username is already taken."), out);
+						socket.close();
+						return;
+					}
+
 					// Try to set the TCP timeout back to 0 now that we've got the correct request.
 					socket.setSoTimeout(0);
 					this.clientAddress = socket.getInetAddress();

server/src/main/java/nl/andrewl/aos2_server/PlayerManager.java

@@ -20,6 +20,7 @@ import org.slf4j.LoggerFactory;
 import java.io.IOException;
 import java.net.DatagramPacket;
 import java.util.*;
+import java.util.regex.Pattern;
 
 /**
  * This component is responsible for managing the set of players connected to
@@ -73,6 +74,21 @@ public class PlayerManager {
 		return players.get(id);
 	}
 
+	public Optional<ServerPlayer> findByIdOrName(String text) {
+		Pattern p = Pattern.compile("\\d+");
+		if (p.matcher(text).matches() && text.length() < 8) {
+			int id = Integer.parseInt(text);
+			return Optional.ofNullable(getPlayer(id));
+		} else {
+			String finalText = text.trim().toLowerCase();
+			List<ServerPlayer> matches = getPlayers().stream()
+					.filter(player -> player.getUsername().trim().toLowerCase().equals(finalText))
+					.toList();
+			if (matches.size() == 1) return Optional.of(matches.get(0));
+			return Optional.empty();
+		}
+	}
+
 	public Collection<ServerPlayer> getPlayers() {
 		return Collections.unmodifiableCollection(players.values());
 	}

server/src/main/java/nl/andrewl/aos2_server/Server.java

@@ -1,5 +1,6 @@
 package nl.andrewl.aos2_server;
 
+import nl.andrewl.aos2_server.cli.ServerCli;
 import nl.andrewl.aos2_server.config.ServerConfig;
 import nl.andrewl.aos2_server.logic.WorldUpdater;
 import nl.andrewl.aos2_server.model.ServerPlayer;
@@ -60,6 +61,7 @@ public class Server implements Runnable {
 		while (running) {
 			acceptClientConnection();
 		}
+		log.info("Shutting down the server.");
 		playerManager.deregisterAll();
 		worldUpdater.shutdown();
 		datagramSocket.close(); // Shuts down the UdpReceiver.
@@ -68,6 +70,20 @@ public class Server implements Runnable {
 		} catch (IOException e) {
 			throw new RuntimeException(e);
 		}
+		log.info("Shutdown complete.");
+	}
+
+	public boolean isRunning() {
+		return running;
+	}
+
+	public void shutdown() {
+		running = false;
+		try {
+			serverSocket.close();
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
 	}
 
 	public void handleUdpMessage(Message msg, DatagramPacket packet) {
@@ -136,6 +152,8 @@ public class Server implements Runnable {
 			configPaths.add(Path.of(args[0].trim()));
 		}
 		ServerConfig cfg = Config.loadConfig(ServerConfig.class, configPaths, new ServerConfig());
-		new Server(cfg).run();
+		Server server = new Server(cfg);
+		new Thread(server).start();
+		ServerCli.start(server);
 	}
 }

server/src/main/java/nl/andrewl/aos2_server/cli/PlayersCommand.java

@@ -0,0 +1,49 @@
+package nl.andrewl.aos2_server.cli;
+
+import nl.andrewl.aos2_server.model.ServerPlayer;
+import nl.andrewl.aos_core.model.Player;
+import picocli.CommandLine;
+
+import java.util.Collection;
+import java.util.Comparator;
+
+@CommandLine.Command(
+		name = "players",
+		description = "Commands for interacting with the players on the server.",
+		mixinStandardHelpOptions = true
+)
+public class PlayersCommand {
+	@CommandLine.ParentCommand ServerCli cli;
+
+	@CommandLine.Command(description = "Lists all online players.")
+	public void list() {
+		var playerManager = cli.server.getPlayerManager();
+		Collection<ServerPlayer> players = playerManager.getPlayers();
+		if (players.isEmpty()) {
+			cli.out.println("There are no players connected to the server.");
+		} else {
+			TablePrinter tp = new TablePrinter(cli.out)
+					.drawBorders(true)
+					.addLine("Id", "Username", "Health", "Position", "Held Item", "Team");
+			players.stream().sorted(Comparator.comparing(Player::getId)).forEachOrdered(player -> {
+				tp.addLine(
+						player.getId(),
+						player.getUsername(),
+						String.format("%.2f / 1.00", player.getHealth()),
+						String.format("x=%.2f, y=%.2f, z=%.2f", player.getPosition().x, player.getPosition().y, player.getPosition().z),
+						player.getInventory().getSelectedItemStack().getType().getName(),
+						player.getTeam() == null ? "None" : player.getTeam().getName()
+				);
+			});
+			tp.println();
+		}
+	}
+
+	@CommandLine.Command(description = "Kicks a player from the server.")
+	public void kick(@CommandLine.Parameters(description = "The id or name of the player to kick.") String playerIdent) {
+		cli.server.getPlayerManager().findByIdOrName(playerIdent)
+				.ifPresentOrElse(player -> {
+					cli.server.getPlayerManager().deregister(player);
+				}, () -> cli.out.println("Player not found."));
+	}
+}

server/src/main/java/nl/andrewl/aos2_server/cli/ServerCli.java

@@ -0,0 +1,102 @@
+package nl.andrewl.aos2_server.cli;
+
+import nl.andrewl.aos2_server.Server;
+import org.fusesource.jansi.AnsiConsole;
+import org.jline.console.SystemRegistry;
+import org.jline.console.impl.Builtins;
+import org.jline.console.impl.SystemRegistryImpl;
+import org.jline.keymap.KeyMap;
+import org.jline.reader.*;
+import org.jline.reader.impl.DefaultParser;
+import org.jline.terminal.Terminal;
+import org.jline.terminal.TerminalBuilder;
+import org.jline.widget.TailTipWidgets;
+import picocli.CommandLine;
+import picocli.shell.jline3.PicocliCommands;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.nio.file.Path;
+
+@CommandLine.Command(
+		name = "",
+		description = "Interactive shell for server commands.",
+		footer = {"", "Press Ctrl-D to exit."},
+		subcommands = {StopCommand.class, PlayersCommand.class}
+)
+public class ServerCli implements Runnable {
+	final Server server;
+	PrintWriter out;
+
+	public ServerCli(Server server) {
+		this.server = server;
+	}
+
+	public void setReader(LineReader reader) {
+		this.out = reader.getTerminal().writer();
+	}
+
+	@Override
+	public void run() {
+		out.println(new CommandLine(this).getUsageMessage());
+	}
+
+	public static void start(Server server) {
+		AnsiConsole.systemInstall();
+		Builtins builtins = new Builtins(Path.of("."), null, null);
+		builtins.rename(Builtins.Command.TTOP, "top");
+		builtins.alias("zle", "widget");
+		builtins.alias("bindkey", "keymap");
+
+		ServerCli baseCommand = new ServerCli(server);
+		PicocliCommands.PicocliCommandsFactory commandsFactory = new PicocliCommands.PicocliCommandsFactory();
+		CommandLine cmd = new CommandLine(baseCommand, commandsFactory);
+		PicocliCommands picocliCommands = new PicocliCommands(cmd);
+		picocliCommands.commandDescription("bleh");
+		Parser parser = new DefaultParser();
+		try (Terminal terminal = TerminalBuilder.builder().build()) {
+			SystemRegistry systemRegistry = new SystemRegistryImpl(parser, terminal, () -> Path.of("."), null);
+			systemRegistry.setCommandRegistries(builtins, picocliCommands);
+			systemRegistry.register("help", picocliCommands);
+
+			LineReader reader = LineReaderBuilder.builder()
+					.terminal(terminal)
+					.completer(systemRegistry.completer())
+					.parser(parser)
+					.variable(LineReader.LIST_MAX, 50)
+					.build();
+			builtins.setLineReader(reader);
+			baseCommand.setReader(reader);
+			commandsFactory.setTerminal(terminal);
+			TailTipWidgets widgets = new TailTipWidgets(reader, systemRegistry::commandDescription, 5, TailTipWidgets.TipType.COMPLETER);
+			widgets.enable();
+			KeyMap<Binding> keyMap = reader.getKeyMaps().get("main");
+			keyMap.bind(new Reference("tailtip-toggle"), KeyMap.alt("s"));
+
+			String prompt = "server> ";
+			String rightPrompt = "HI";
+
+			String line;
+			while (server.isRunning()) {
+				try {
+					systemRegistry.cleanUp();
+					line = reader.readLine(prompt, rightPrompt, (MaskingCallback) null, null);
+					systemRegistry.execute(line);
+				} catch (UserInterruptException e) {
+					// Ignore
+				} catch (EndOfFileException e) {
+					break;
+				} catch (Exception e) {
+					systemRegistry.trace(e);
+				}
+			}
+			// If the user exits the CLI without calling "stop", we will shut down the server automatically.
+			if (server.isRunning()) {
+				server.shutdown();
+			}
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+		AnsiConsole.systemUninstall();
+	}
+}

server/src/main/java/nl/andrewl/aos2_server/cli/StopCommand.java

@@ -0,0 +1,17 @@
+package nl.andrewl.aos2_server.cli;
+
+import picocli.CommandLine;
+
+@CommandLine.Command(
+		name = "stop",
+		description = "Stops the server.",
+		mixinStandardHelpOptions = true
+)
+public class StopCommand implements Runnable {
+	@CommandLine.ParentCommand ServerCli cli;
+
+	@Override
+	public void run() {
+		cli.server.shutdown();
+	}
+}

server/src/main/java/nl/andrewl/aos2_server/cli/TablePrinter.java

@@ -0,0 +1,136 @@
+package nl.andrewl.aos2_server.cli;
+
+import java.io.PrintWriter;
+import java.util.ArrayList;
+import java.util.List;
+
+public class TablePrinter {
+	private final PrintWriter out;
+	private final List<List<String>> lines = new ArrayList<>();
+	private boolean drawBorders = false;
+	private final int[] padding = new int[]{1, 1, 0, 0};
+
+	public TablePrinter(PrintWriter out) {
+		this.out = out;
+	}
+
+	public TablePrinter addLine(List<String> line) {
+		lines.add(line);
+		return this;
+	}
+
+	public TablePrinter addLine(Object... objects) {
+		List<String> line = new ArrayList<>(objects.length);
+		for (var obj : objects) {
+			line.add(obj.toString());
+		}
+		return addLine(line);
+	}
+
+	public TablePrinter drawBorders(boolean drawBorders) {
+		this.drawBorders = drawBorders;
+		return this;
+	}
+
+	public TablePrinter padding(int left, int right, int top, int bottom) {
+		this.padding[0] = left;
+		this.padding[1] = right;
+		this.padding[2] = top;
+		this.padding[3] = bottom;
+		return this;
+	}
+
+	public void println() {
+		int rowCount = lines.size();
+		int colCount = lines.stream().mapToInt(List::size).max().orElse(0);
+		if (rowCount == 0 || colCount == 0) out.println();
+
+		int[] colSizes = new int[colCount];
+		for (int i = 0; i < colCount; i++) {
+			final int columnIndex = i;
+			colSizes[i] = lines.stream().mapToInt(line -> {
+				if (columnIndex >= line.size()) return 0;
+				return line.get(columnIndex).length();
+			}).max().orElse(0);
+		}
+
+		for (int row = 0; row < rowCount; row++) {
+			// Row top border.
+			if (drawBorders) {
+				out.print('+');
+				for (int col = 0; col < colCount; col++) {
+					out.print("-".repeat(colSizes[col] + leftPadding() + rightPadding()));
+					out.print('+');
+				}
+				out.println();
+			}
+			// Top padding rows.
+			for (int p = 0; p < topPadding(); p++) {
+				for (int col = 0; col < colCount; col++) {
+					if (drawBorders) out.print('|');
+					out.print(" ".repeat(leftPadding() + colSizes[col] + rightPadding()));
+				}
+				if (drawBorders) out.print('|');
+				out.println();
+			}
+			// Column values.
+			for (int col = 0; col < colCount; col++) {
+				String value = getValueAt(row, col);
+				if (drawBorders) out.print('|');
+				out.print(" ".repeat(leftPadding()));
+				out.print(value);
+				out.print(" ".repeat(colSizes[col] - value.length() + rightPadding()));
+			}
+			if (drawBorders) out.print('|');
+			out.println();
+			// Bottom padding rows.
+			for (int p = 0; p < bottomPadding(); p++) {
+				for (int col = 0; col < colCount; col++) {
+					if (drawBorders) out.print('|');
+					out.print(" ".repeat(leftPadding() + colSizes[col] + rightPadding()));
+				}
+				if (drawBorders) out.print('|');
+				out.println();
+			}
+
+			// Last row bottom border.
+			if (row == rowCount - 1 && drawBorders) {
+				out.print('+');
+				for (int col = 0; col < colCount; col++) {
+					out.print("-".repeat(colSizes[col] + leftPadding() + rightPadding()));
+					out.print('+');
+				}
+				out.println();
+			}
+		}
+	}
+
+	private String getValueAt(int row, int col) {
+		if (row < lines.size()) {
+			List<String> line = lines.get(row);
+			if (col < line.size()) {
+				return line.get(col);
+			} else {
+				return "";
+			}
+		} else {
+			return "";
+		}
+	}
+
+	private int leftPadding() {
+		return padding[0];
+	}
+
+	private int rightPadding() {
+		return padding[1];
+	}
+
+	private int topPadding() {
+		return padding[2];
+	}
+
+	private int bottomPadding() {
+		return padding[3];
+	}
+}