diff --git a/README.md b/README.md
index f1a86da..e6929b8 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,6 @@
 
 <U>**device uuid 무조건 바꾸시오.**</U>
 
-자바21에 추가된 virtual thread 사용하도록 바꾸는중...
-
 ## Example
 
 ![ex](./ex.png)
@@ -80,6 +78,8 @@ jar 파일은 build/libs 디렉터리 안에 생성됩니다.
 
 ## Usage
 
+자바21 이상 필요합니다.
+
 첫 로그인시에 기기등록이 필요합니다. 콘솔창에 방법 나오니 따라하세요.
 
 로그인하면 로그인 정보(토큰 등)가 email_deviceName 폴더 안에 저장됩니다. 서버 연결이 안되면 삭제하고 시도하세요.
diff --git a/build.gradle b/build.gradle
index 3142ddf..2e0430b 100644
--- a/build.gradle
+++ b/build.gradle
@@ -4,6 +4,8 @@ plugins {
 
 group = 'com.github.netricecake'
 version = '1.0-SNAPSHOT'
+sourceCompatibility = '21'
+targetCompatibility = '21'
 
 jar {
     manifest {
diff --git a/src/main/java/com/github/netricecake/kakao/LocoSocketHandlerImpl.java b/src/main/java/com/github/netricecake/kakao/LocoSocketHandlerImpl.java
index 3801547..883b51f 100644
--- a/src/main/java/com/github/netricecake/kakao/LocoSocketHandlerImpl.java
+++ b/src/main/java/com/github/netricecake/kakao/LocoSocketHandlerImpl.java
@@ -16,12 +16,10 @@ import com.github.netricecake.loco.packet.outbound.room.InfoLinkOut;
 import com.github.netricecake.loco.packet.outbound.message.MessageOut;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonObject;
-import lombok.Getter;
 
 public class LocoSocketHandlerImpl extends LocoSocketHandler {
 
-    @Getter
-    private TalkClient client;
+    private final TalkClient client;
 
     public LocoSocketHandlerImpl(TalkClient client) {
         this.client = client;
@@ -41,7 +39,9 @@ public class LocoSocketHandlerImpl extends LocoSocketHandler {
             Member member = room.getMembers().get(in.getAuthorId());
 
             Message msg = new Message(in.getLogId(), room, member, in.getType(), in.getMessage(), in.getAttachment());
-            client.getTalkHandler().onMessage(msg);
+            Thread.ofVirtual().start(() -> {
+                client.getTalkHandler().onMessage(msg);
+            });
         } else if (packet.getMethod().equals("NEWMEM")) {
             NewMemIn in = new NewMemIn();
             in.fromBson(packet.getBody());
@@ -50,7 +50,9 @@ public class LocoSocketHandlerImpl extends LocoSocketHandler {
 
             ChatRoom room = client.getChatRooms().get(in.getChatId());
             if (!room.getType().equals("OM")) return;
-            client.getTalkHandler().onNewMember(room, room.getMembers().get(in.getUserId()));
+            Thread.ofVirtual().start(() -> {
+                client.getTalkHandler().onNewMember(room, room.getMembers().get(in.getUserId()));
+            });
         } else if (packet.getMethod().equals("DELMEM")) {
             DelMemIn in = new DelMemIn();
             in.fromBson(packet.getBody());
@@ -58,7 +60,9 @@ public class LocoSocketHandlerImpl extends LocoSocketHandler {
 
             ChatRoom room = client.getChatRooms().get(in.getChatId());
             if (!room.getType().equals("OM")) return;
-            client.getTalkHandler().onDelMember(room, new Member(in.getUserId(), in.getNickname(), 2));
+            Thread.ofVirtual().start(() -> {
+                client.getTalkHandler().onDelMember(room, new Member(in.getUserId(), in.getNickname(), 2));
+            });
             room.getMembers().remove(in.getUserId());
         } else if (packet.getMethod().equals("SYNCLINKPF")) {
             SyncLinkPfIn si = new SyncLinkPfIn();
diff --git a/src/main/java/com/github/netricecake/kakao/TalkClient.java b/src/main/java/com/github/netricecake/kakao/TalkClient.java
index 0aa8958..02bb28c 100644
--- a/src/main/java/com/github/netricecake/kakao/TalkClient.java
+++ b/src/main/java/com/github/netricecake/kakao/TalkClient.java
@@ -36,14 +36,14 @@ import java.util.concurrent.Executors;
 
 public class TalkClient {
 
-    private String email;
-    private String password;
-    private String deviceName;
-    private String deviceUuid;
-    private String sessionDir;
+    private final String email;
+    private final String password;
+    private final String deviceName;
+    private final String deviceUuid;
+    private final String sessionDir;
 
     @Getter
-    private Map<Long, ChatRoom> chatRooms = new HashMap<>();
+    private final Map<Long, ChatRoom> chatRooms = new HashMap<>();
 
     @Getter
     protected boolean connected;
diff --git a/src/main/java/com/github/netricecake/loco/codec/SecureLayerCodec.java b/src/main/java/com/github/netricecake/loco/codec/SecureLayerCodec.java
index 0fab3da..395e418 100644
--- a/src/main/java/com/github/netricecake/loco/codec/SecureLayerCodec.java
+++ b/src/main/java/com/github/netricecake/loco/codec/SecureLayerCodec.java
@@ -9,7 +9,7 @@ import java.util.List;
 
 public class SecureLayerCodec extends MessageToMessageCodec<byte[], byte[]> {
 
-    private CryptoManager cryptoManager;
+    private final CryptoManager cryptoManager;
 
     private int currentLength = -1;
     private byte[] buffer = new byte[0];
@@ -20,6 +20,7 @@ public class SecureLayerCodec extends MessageToMessageCodec<byte[], byte[]> {
 
     @Override
     protected void encode(ChannelHandlerContext channelHandlerContext, byte[] bytes, List<Object> list) throws Exception {
+        // TODO 길이 길면 짤라서 암호화해서 보내야됨
         byte[] encryptedBody = cryptoManager.encryptMessage(bytes);
         byte[] packet = ByteUtil.concatBytes(ByteUtil.intToByteArrayLE(encryptedBody.length), encryptedBody);
         list.add(packet);
diff --git a/src/main/java/com/github/netricecake/loco/crypto/CryptoManager.java b/src/main/java/com/github/netricecake/loco/crypto/CryptoManager.java
index 792e951..ab39de3 100644
--- a/src/main/java/com/github/netricecake/loco/crypto/CryptoManager.java
+++ b/src/main/java/com/github/netricecake/loco/crypto/CryptoManager.java
@@ -55,10 +55,9 @@ public class CryptoManager {
             byte[] length = ByteUtil.intToByteArrayLE(HANDSHAKE_BODY_SIZE);
             return ByteUtil.concatBytes(length, ByteUtil.intToByteArrayLE(RSA_LOCO_HEADER), ByteUtil.intToByteArrayLE(AES_LOCO_HEADER), encryptedKey);
         } catch (Exception e) {}
-        return new byte[0];
+        return null;
     }
 
-    // 바디 사이즈가 131067가 최대인거 같은데 잘 모르겠음
     public byte[] encryptMessage(byte[] message) {
         try {
             byte[] nonce = new byte[AES_NONCE_SIZE];
@@ -67,7 +66,7 @@ public class CryptoManager {
             cipher.init(Cipher.ENCRYPT_MODE, aesKey, new GCMParameterSpec(AES_KEY_SIZE, nonce));
             return ByteUtil.concatBytes(nonce, cipher.doFinal(message));
         } catch (Exception e) {}
-        return new byte[0];
+        return null;
     }
 
     public byte[] decryptMessage(byte[] message) {
@@ -77,7 +76,7 @@ public class CryptoManager {
             cipher.init(Cipher.DECRYPT_MODE, aesKey,  new GCMParameterSpec(AES_KEY_SIZE, nonce));
             return cipher.doFinal(ByteUtil.sliceBytes(message, AES_NONCE_SIZE, message.length - nonce.length));
         } catch (Exception e) {}
-        return new byte[0];
+        return null;
     }
 
 }