fix(multiplayer): restore LocalServerBroadcaster and impl port forwarding.

HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/LocalServerBroadcaster.java

@@ -0,0 +1,127 @@
+/*
+ * Hello Minecraft! Launcher
+ * Copyright (C) 2022  huangyuhui <huanghongxun2008@126.com> and contributors
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.jackhuang.hmcl.ui.multiplayer;
+
+import org.jackhuang.hmcl.util.Lang;
+
+import java.io.IOException;
+import java.net.*;
+import java.nio.ByteBuffer;
+import java.nio.channels.ServerSocketChannel;
+import java.nio.channels.SocketChannel;
+import java.nio.charset.StandardCharsets;
+import java.util.logging.Level;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import static org.jackhuang.hmcl.util.Logging.LOG;
+import static org.jackhuang.hmcl.util.i18n.I18n.i18n;
+
+public class LocalServerBroadcaster implements AutoCloseable {
+    private final String address;
+    private final ThreadGroup threadGroup = new ThreadGroup("JoinSession");
+
+    private boolean running = true;
+
+    public LocalServerBroadcaster(String address) {
+        this.address = address;
+        this.threadGroup.setDaemon(true);
+    }
+
+    @Override
+    public void close() {
+        running = false;
+        threadGroup.interrupt();
+    }
+
+    public static final Pattern ADDRESS_PATTERN = Pattern.compile("^\\s*(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}):(\\d{1,5})\\s*$");
+
+    public void start() {
+        Thread forwardPortThread = new Thread(threadGroup, this::forwardPort, "ForwardPort");
+        forwardPortThread.start();
+    }
+
+    private void forwardPort() {
+        try {
+            Matcher matcher = ADDRESS_PATTERN.matcher(address);
+            if (!matcher.find()) {
+                throw new MalformedURLException();
+            }
+            try (SocketChannel forwardingSocket = SocketChannel.open(new InetSocketAddress(matcher.group(0), Lang.parseInt(matcher.group(1), 0)));
+                 ServerSocketChannel serverSocket = ServerSocketChannel.open()) {
+                serverSocket.socket().bind(null);
+
+                Thread broadcastMOTDThread = new Thread(threadGroup, () -> broadcastMOTD(serverSocket.socket().getLocalPort()), "BroadcastMOTD");
+                broadcastMOTDThread.start();
+
+                while (running) {
+                    SocketChannel forwardedSocket = serverSocket.accept();
+                    new Thread(threadGroup, () -> forwardTraffic(forwardingSocket, forwardedSocket), "Forward S->D").start();
+                    new Thread(threadGroup, () -> forwardTraffic(forwardedSocket, forwardingSocket), "Forward D->S").start();
+                }
+            }
+        } catch (IOException e) {
+            LOG.log(Level.WARNING, "Error in forwarding port", e);
+            threadGroup.interrupt();
+        }
+    }
+
+    private void forwardTraffic(SocketChannel src, SocketChannel dest) {
+        try {
+            ByteBuffer buf = ByteBuffer.allocate(1024);
+            while (true) {
+                int len = src.read(buf);
+                if (len < 0) break;
+                dest.write(buf);
+            }
+        } catch (IOException e) {
+            LOG.log(Level.WARNING, "Disconnected", e);
+        }
+    }
+
+    private void broadcastMOTD(int port) {
+        DatagramSocket socket;
+        InetAddress broadcastAddress;
+        try {
+            socket = new DatagramSocket();
+            broadcastAddress = InetAddress.getByName("224.0.2.60");
+        } catch (IOException e) {
+            LOG.log(Level.WARNING, "Failed to create datagram socket", e);
+            return;
+        }
+
+        while (running) {
+            try {
+                byte[] data = String.format("[MOTD]%s[/MOTD][AD]%d[/AD]", i18n("multiplayer.session.name.motd"), port).getBytes(StandardCharsets.UTF_8);
+                DatagramPacket packet = new DatagramPacket(data, 0, data.length, broadcastAddress, 4445);
+                socket.send(packet);
+                LOG.finest("Broadcast server 0.0.0.0:" + port);
+            } catch (IOException e) {
+                LOG.log(Level.WARNING, "Failed to send motd packet", e);
+            }
+
+            try {
+                Thread.sleep(1500);
+            } catch (InterruptedException ignored) {
+                return;
+            }
+        }
+
+        socket.close();
+    }
+}

HMCL/src/main/resources/assets/lang/I18N.properties

@@ -852,6 +852,7 @@ multiplayer.exit=HiPer exited unexpectedly with exit code %d
 multiplayer.hint=The multiplayer online function is in the experimental stage, if you have any questions, please go to mcer.cn to give feedback
 multiplayer.powered_by=This service is provided under the license of (<a href="https://mcer.cn">Matrix Lab</a>)<a href\="https\://hmcl.huangyuhui.net/api/redirect/multiplayer-agreement" >License Agreement</a>
 multiplayer.report=Illegal and Violation Report
+multiplayer.session.name.motd=HMCL Multiplayer Session
 multiplayer.token=Token
 multiplayer.token.apply=Apply for a token
 multiplayer.token.expired=HiPer certificate expired, please restart HMCL and try again.