diff --git a/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerManager.java b/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerManager.java
index 7c15f012c..5de8eec03 100644
--- a/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerManager.java
+++ b/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerManager.java
@@ -17,7 +17,76 @@
  */
 package org.jackhuang.hmcl.ui.multiplayer;
 
+import org.jackhuang.hmcl.Metadata;
+import org.jackhuang.hmcl.game.Artifact;
+import org.jackhuang.hmcl.task.FileDownloadTask;
+import org.jackhuang.hmcl.task.Task;
+import org.jackhuang.hmcl.task.TaskExecutor;
+import org.jackhuang.hmcl.ui.Controllers;
+import org.jackhuang.hmcl.ui.construct.TaskExecutorDialogPane;
+import org.jackhuang.hmcl.util.io.NetworkUtils;
+import org.jackhuang.hmcl.util.platform.ManagedProcess;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+
+import static org.jackhuang.hmcl.util.i18n.I18n.i18n;
+
+/**
+ * Cato Management.
+ */
 public class MultiplayerManager {
+    private static final String CATO_DOWNLOAD_URL = "https://hmcl.huangyuhui.net/maven/";
+    private static final String CATO_VERSION = "2021-09-01";
+    private static final Artifact CATO_ARTIFACT = new Artifact("cato", "cato", CATO_VERSION);
+
+    public static void fetchIdAndToken() {
+        // TODO
+    }
+
+    public static Task<Void> downloadCato() {
+        return new FileDownloadTask(
+                NetworkUtils.toURL(CATO_DOWNLOAD_URL + CATO_ARTIFACT.getPath()),
+                getCatoExecutable().toFile()
+        );
+    }
+
+    public static Path getCatoExecutable() {
+        return CATO_ARTIFACT.getPath(Metadata.HMCL_DIRECTORY);
+    }
+
+    public static ManagedProcess joinRoom(String token, String peer, String localAddress, String remoteAddress) throws IOException {
+        Path exe = getCatoExecutable();
+        if (!Files.isRegularFile(exe)) {
+            throw new IllegalStateException("Cato file not found");
+        }
+        String[] commands = new String[]{exe.toString(), "--peer", peer, "--from", localAddress, "--to", remoteAddress};
+        Process process = new ProcessBuilder()
+                .command(commands)
+                .inheritIO()
+                .start();
+        ManagedProcess managedProcess = new ManagedProcess(process, Arrays.asList(commands));
+        managedProcess.getProcess().getOutputStream().write(token.getBytes(StandardCharsets.UTF_8));
+        return managedProcess;
+    }
+
+    public static ManagedProcess createRoom(String token, String peer, String localAddress) throws IOException {
+        Path exe = getCatoExecutable();
+        if (!Files.isRegularFile(exe)) {
+            throw new IllegalStateException("Cato file not found");
+        }
+        String[] commands = new String[]{exe.toString(), "--peer", peer, "--from", localAddress};
+        Process process = new ProcessBuilder()
+                .command(commands)
+                .inheritIO()
+                .start();
+        ManagedProcess managedProcess = new ManagedProcess(process, Arrays.asList(commands));
+        managedProcess.getProcess().getOutputStream().write(token.getBytes(StandardCharsets.UTF_8));
+        return managedProcess;
+    }
 
     enum State {
         DISCONNECTED,
diff --git a/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerPage.java b/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerPage.java
index e3edf4e58..c8c0a1b73 100644
--- a/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerPage.java
+++ b/HMCL/src/main/java/org/jackhuang/hmcl/ui/multiplayer/MultiplayerPage.java
@@ -19,14 +19,13 @@ package org.jackhuang.hmcl.ui.multiplayer;
 
 import de.javawi.jstun.test.DiscoveryInfo;
 import de.javawi.jstun.test.DiscoveryTest;
-import javafx.beans.property.ObjectProperty;
-import javafx.beans.property.ReadOnlyObjectProperty;
-import javafx.beans.property.ReadOnlyObjectWrapper;
-import javafx.beans.property.SimpleObjectProperty;
+import javafx.beans.property.*;
 import javafx.scene.control.Control;
 import javafx.scene.control.Skin;
 import org.jackhuang.hmcl.task.Schedulers;
 import org.jackhuang.hmcl.task.Task;
+import org.jackhuang.hmcl.task.TaskExecutor;
+import org.jackhuang.hmcl.ui.Controllers;
 import org.jackhuang.hmcl.ui.decorator.DecoratorPage;
 
 import static org.jackhuang.hmcl.util.i18n.I18n.i18n;
@@ -39,6 +38,7 @@ public class MultiplayerPage extends Control implements DecoratorPage {
 
     public MultiplayerPage() {
         testNAT();
+        downloadCatoIfNecessary();
     }
 
     @Override
@@ -66,7 +66,7 @@ public class MultiplayerPage extends Control implements DecoratorPage {
         return natState.getReadOnlyProperty();
     }
 
-    public void testNAT() {
+    private void testNAT() {
         Task.supplyAsync(() -> {
             DiscoveryTest tester = new DiscoveryTest(null, 0, "stun.qq.com", 3478);
             return tester.test();
@@ -79,6 +79,19 @@ public class MultiplayerPage extends Control implements DecoratorPage {
         }).start();
     }
 
+    private void downloadCatoIfNecessary() {
+        if (!MultiplayerManager.getCatoExecutable().toFile().exists()) {
+            setDisabled(true);
+            TaskExecutor executor = MultiplayerManager.downloadCato()
+                    .thenRunAsync(Schedulers.javafx(), () -> {
+                        setDisabled(false);
+                    }).executor(false);
+            Controllers.taskDialog(executor, i18n("multiplayer.download"));
+        } else {
+            setDisabled(false);
+        }
+    }
+
     @Override
     public ReadOnlyObjectProperty<State> stateProperty() {
         return state;