diff --git a/ClientTester/EchoClientTester/EchoDummyService/DummyClientService.cs b/ClientTester/EchoClientTester/EchoDummyService/DummyClientService.cs
index b3994dc..1c7020f 100644
--- a/ClientTester/EchoClientTester/EchoDummyService/DummyClientService.cs
+++ b/ClientTester/EchoClientTester/EchoDummyService/DummyClientService.cs
@@ -1,17 +1,20 @@
-using LiteNetLib.Utils;
+using LiteNetLib;
 using Serilog;
 
 namespace ClientTester.EchoDummyService;
 
 public class DummyClientService
 {
-    private readonly List<DummyClients> _clients;
-    private readonly int _sendInterval;
+    private readonly List<DummyClients> clients;
+    private readonly int sendInterval;
+
+    // 모든거 강종
+    public event Action? OnAllDisconnected;
 
     public DummyClientService(int count, string ip, int port, string key, int sendIntervalMs = 1000)
     {
-        _sendInterval = sendIntervalMs;
-        _clients = Enumerable.Range(0, count)
+        sendInterval = sendIntervalMs;
+        clients = Enumerable.Range(0, count)
             .Select(i => new DummyClients(i, ip, port, key))
             .ToList();
 
@@ -30,62 +33,100 @@ public class DummyClientService
     {
         while (!ct.IsCancellationRequested)
         {
-            foreach (var c in _clients)
+            foreach (DummyClients c in clients)
+            {
                 c.PollEvents();
+            }
 
-            try   { await Task.Delay(15, ct); }
-            catch (OperationCanceledException) { break; }
+            try
+            {
+                await Task.Delay(15, ct);
+            }
+            catch (OperationCanceledException)
+            {
+                break;
+            }
         }
     }
 
     private async Task SendLoopAsync(CancellationToken ct)
     {
-        try   { await Task.Delay(500, ct); }
-        catch (OperationCanceledException) { return; }
+        try
+        {
+            await Task.Delay(500, ct);
+        }
+        catch (OperationCanceledException)
+        {
+            return;
+        }
 
         int tick = 0;
 
         while (!ct.IsCancellationRequested)
         {
             int sent = 0;
+            int total = clients.Count;
 
-            foreach (var client in _clients)
+            foreach (DummyClients client in clients)
             {
                 client.SendPing();
-                if (client.Peer != null) sent++;
+                if (client.peer != null)
+                {
+                    sent++;
+                }
+                else
+                {
+                    total--;
+                }
             }
 
-            Log.Information("[TICK {Tick:000}] {Sent}/{Total} 전송", tick, sent, _clients.Count);
+            if (total == 0)
+            {
+                Log.Information("All Disconnect Clients");
+                OnAllDisconnected?.Invoke();
+                break;
+            }
+
+            Log.Information("[TICK {Tick:000}] {Sent}/{Total} 전송", tick, sent, total);
             tick++;
 
-            try   { await Task.Delay(_sendInterval, ct); }
-            catch (OperationCanceledException) { break; }
+            try
+            {
+                await Task.Delay(sendInterval, ct);
+            }
+            catch (OperationCanceledException)
+            {
+                break;
+            }
         }
     }
 
     public void PrintStats()
     {
-        int  totalSent = 0, totalRecv = 0;
-        int  connected = 0;
+        int totalSent = 0, totalRecv = 0;
+        int connected = 0;
 
-        Log.Information("════════════ Performance Report ════════════");
+        Log.Information("───────────── Performance Report ─────────────");
 
         double totalAvgRtt = 0;
 
-        foreach (var c in _clients)
+        foreach (DummyClients c in clients)
         {
-            var   stats   = c.Peer?.Statistics;
-            long  loss    = stats?.PacketLoss        ?? 0;
+            NetStatistics? stats = c.peer?.Statistics;
+            long loss = stats?.PacketLoss ?? 0;
             float lossPct = stats?.PacketLossPercent ?? 0f;
 
             Log.Information(
                 "[Client {ClientId:00}] Sent={Sent} Recv={Recv} | Loss={Loss}({LossPct:F1}%) AvgRTT={AvgRtt:F3}ms LastRTT={LastRtt:F3}ms",
-                c.ClientId, c.SentCount, c.ReceivedCount, loss, lossPct, c.AvgRttMs, c.LastRttMs);
+                c.clientId, c.SentCount, c.ReceivedCount, loss, lossPct, c.AvgRttMs, c.LastRttMs);
 
-            totalSent    += c.SentCount;
-            totalRecv    += c.ReceivedCount;
-            totalAvgRtt  += c.AvgRttMs;
-            if (c.Peer != null) connected++;
+            totalSent += c.SentCount;
+            totalRecv += c.ReceivedCount;
+            totalAvgRtt += c.AvgRttMs;
+            if (c.peer != null)
+            {
+                connected++;
+            }
         }
 
         double avgRtt = connected > 0 ? totalAvgRtt / connected : 0;
@@ -93,14 +134,16 @@ public class DummyClientService
         Log.Information("────────────────────────────────────────────");
         Log.Information(
             "[TOTAL] Sent={Sent} Recv={Recv} Connected={Connected}/{Total} AvgRTT={AvgRtt:F3}ms",
-            totalSent, totalRecv, connected, _clients.Count, avgRtt);
-        Log.Information("════════════════════════════════════════════");
+            totalSent, totalRecv, connected, clients.Count, avgRtt);
+        Log.Information("────────────────────────────────────────────");
     }
 
     public void Stop()
     {
-        foreach (var c in _clients)
+        foreach (DummyClients c in clients)
+        {
             c.Stop();
+        }
 
         Log.Information("[SERVICE] 모든 클라이언트 종료됨.");
     }
diff --git a/ClientTester/EchoClientTester/EchoDummyService/DummyClients.cs b/ClientTester/EchoClientTester/EchoDummyService/DummyClients.cs
index 8af7723..6dec658 100644
--- a/ClientTester/EchoClientTester/EchoDummyService/DummyClients.cs
+++ b/ClientTester/EchoClientTester/EchoDummyService/DummyClients.cs
@@ -1,4 +1,5 @@
 using System.Diagnostics;
+using ClientTester.Packet;
 using LiteNetLib;
 using LiteNetLib.Utils;
 using Serilog;
@@ -7,82 +8,112 @@ namespace ClientTester.EchoDummyService;
 
 public class DummyClients
 {
-    public NetManager Manager;
-    public EventBasedNetListener Listener;
-    public NetPeer? Peer;
-    public int ClientId;
+    public NetManager manager;
+    public EventBasedNetListener listener;
+    public NetPeer? peer;
+    public int clientId;
 
     // seq → 송신 타임스탬프 (Stopwatch tick)
-    private readonly Dictionary<int, long> _pendingPings = new();
-    private int _seqNumber;
+    private readonly Dictionary<int, long> pendingPings = new();
+    private int seqNumber;
 
     // 통계
-    public int SentCount;
-    public int ReceivedCount;
-    public double LastRttMs;
-    public double TotalRttMs;
-    public int RttCount;
+    public int SentCount
+    {
+        set;
+        get;
+    }
+    public int ReceivedCount
+    {
+        set;
+        get;
+    }
+    public double LastRttMs
+    {
+        set;
+        get;
+    }
+    public double TotalRttMs
+    {
+        set;
+        get;
+    }
+    public int RttCount
+    {
+        set;
+        get;
+    }
 
     public DummyClients(int clientId, string ip, int port, string key)
     {
-        ClientId = clientId;
-        Listener = new EventBasedNetListener();
-        Manager  = new NetManager(Listener);
+        this.clientId = clientId;
+        listener = new EventBasedNetListener();
+        manager  = new NetManager(listener);
 
-        Listener.PeerConnectedEvent += peer =>
+        listener.PeerConnectedEvent += netPeer =>
         {
-            Peer = peer;
-            Log.Information("[Client {ClientId:00}] 연결됨", ClientId);
+            peer = netPeer;
+            Log.Information("[Client {ClientId:00}] 연결됨", this.clientId);
         };
 
-        Listener.NetworkReceiveEvent += (peer, reader, channel, deliveryMethod) =>
+        listener.NetworkReceiveEvent += (peer, reader, channel, deliveryMethod) =>
         {
-            var msg = reader.GetString();
+            string? msg = reader.GetString();
 
-            // "ack:seq:{seqNum}" 파싱
-            var parts = msg.Split(':');
-            if (parts.Length == 3 && parts[0] == "ack" && parts[1] == "seq"
-                && int.TryParse(parts[2], out int seq)
-                && _pendingPings.TryGetValue(seq, out long sentTick))
+            string[] parts = msg.Split(':');
+            if (parts.Length == 3 && parts[0] == "ack" && parts[1] == "seq" && int.TryParse(parts[2], out int seq) && pendingPings.TryGetValue(seq, out long sentTick))
             {
-                double rttMs = (Stopwatch.GetTimestamp() - sentTick)
-                               * 1000.0 / Stopwatch.Frequency;
+                double rttMs = (Stopwatch.GetTimestamp() - sentTick) * 1000.0 / Stopwatch.Frequency;
                 LastRttMs  = rttMs;
                 TotalRttMs += rttMs;
                 RttCount++;
-                _pendingPings.Remove(seq);
+                pendingPings.Remove(seq);
             }
 
             ReceivedCount++;
             reader.Recycle();
         };
 
-        Listener.PeerDisconnectedEvent += (peer, info) =>
+        listener.PeerDisconnectedEvent += (peer, info) =>
         {
-            Log.Warning("[Client {ClientId:00}] 연결 끊김: {Reason}", ClientId, info.Reason);
-            Peer = null;
+            Log.Warning("[Client {ClientId:00}] 연결 끊김: {Reason}", this.clientId, info.Reason);
+            this.peer = null;
         };
 
-        Manager.Start();
-        Manager.Connect(ip, port, key);
+        manager.Start();
+        manager.Connect(ip, port, key);
     }
 
     public void SendPing()
     {
-        if (Peer is null) return;
+        if (peer == null)
+        {
+            return;
+        }
 
-        int seq = _seqNumber++;
-        _pendingPings[seq] = Stopwatch.GetTimestamp();
+        int seq = seqNumber++;
+        pendingPings[seq] = Stopwatch.GetTimestamp();
 
-        var writer = new NetDataWriter();
-        writer.Put($"seq:{seq}");
-        Peer.Send(writer, DeliveryMethod.ReliableOrdered);
+        NetDataWriter writer = new NetDataWriter();
+        PacketHeader packetHeader = new PacketHeader();
+        packetHeader.Code = 0;
+        packetHeader.BodyLength = $"seq:{seq}".Length;
+        writer.Put((short)packetHeader.Code);
+        writer.Put((short)packetHeader.BodyLength);
+        writer.Put($"Echo seq:{seq}");
+        peer.Send(writer, DeliveryMethod.ReliableOrdered);
         SentCount++;
     }
 
     public double AvgRttMs => RttCount > 0 ? TotalRttMs / RttCount : 0.0;
 
-    public void PollEvents() => Manager.PollEvents();
+    public void PollEvents()
+    {
+        manager.PollEvents();
+    }
 
-    public void Stop() => Manager.Stop();
+    public void Stop()
+    {
+        manager.Stop();
+    }
 }
diff --git a/ClientTester/EchoClientTester/Packet/PacketBody.cs b/ClientTester/EchoClientTester/Packet/PacketBody.cs
index a3fbcc1..e03683d 100644
--- a/ClientTester/EchoClientTester/Packet/PacketBody.cs
+++ b/ClientTester/EchoClientTester/Packet/PacketBody.cs
@@ -1,3 +1,5 @@
+#pragma warning disable CS8618
+
 using ProtoBuf;
 
 namespace ClientTester.Packet;
@@ -164,7 +166,7 @@ public class IntoLobbyPacket
     {
         get;
         set;
-    }
+    } = null!;
 }
 
 // EXIT_LOBBY
diff --git a/ClientTester/EchoClientTester/Packet/PacketHeader.cs b/ClientTester/EchoClientTester/Packet/PacketHeader.cs
index b95aa68..3512a8b 100644
--- a/ClientTester/EchoClientTester/Packet/PacketHeader.cs
+++ b/ClientTester/EchoClientTester/Packet/PacketHeader.cs
@@ -1,55 +1,55 @@
 namespace ClientTester.Packet;
 
-public enum PacketCode
+public enum PacketCode : short
 {
     NONE,
     // 초기 클라이언트 시작시 jwt토큰 받아옴
     RECV_TOKEN,
     // jwt토큰 검증후 게임에 들어갈지 말지 (내 데이터도 전송)
     LOAD_GAME,
-    
+
     // 마을(로비)진입시 모든 데이터 로드
     INTO_LOBBY,
-    
+
     // 로비 나가기
     EXIT_LOBBY,
-    
+
     // 인스턴스 던전 입장
     INTO_INSTANCE,
-    
+
     // 결과 보상
     REWARD_INSTANCE,
-    
+
     // 보스전 (시작, 종료)
     UPDATE_BOSS,
-    
+
     // 인스턴스 던전 퇴장
     EXIT_INSTANCE,
-    
+
     // 파티 (생성, 삭제)
     UPDATE_PARTY,
-    
+
     // 파티 유저 업데이트(추가 삭제)
     UPDATE_USER_PARTY,
-    
+
     // 플레이어 위치, 방향
     TRANSFORM_PLAYER,
-    
+
     // 플레이어 행동 업데이트
     ACTION_PLAYER,
-    
+
     // 플레이어 스테이트 업데이트
     STATE_PLAYER,
-    
+
     // NPC 위치, 방향
     TRANSFORM_NPC,
-    
+
     // NPC 행동 업데이트
     ACTION_NPC,
-    
+
     // NPC 스테이트 업데이트
     STATE_NPC,
-    
+
     // 데미지 UI 전달
     DAMAGE
 }
@@ -58,4 +58,4 @@ public class PacketHeader
 {
     public PacketCode Code;
     public int BodyLength;
-}
\ No newline at end of file
+}
diff --git a/ClientTester/EchoClientTester/Program.cs b/ClientTester/EchoClientTester/Program.cs
index 73aed81..c57acc1 100644
--- a/ClientTester/EchoClientTester/Program.cs
+++ b/ClientTester/EchoClientTester/Program.cs
@@ -1,28 +1,37 @@
 using ClientTester.EchoDummyService;
 using Serilog;
 
-Log.Logger = new LoggerConfiguration()
-    .WriteTo.Console()
-    .CreateLogger();
-
-const string SERVER_IP = "localhost";
-const int SERVER_PORT = 9500;
-const string CONNECTION_KEY = "game";
-const int CLIENT_COUNT = 1000;
-
-var cts = new CancellationTokenSource();
-Console.CancelKeyPress += (_, e) =>
+class EcoClientTester
 {
-    e.Cancel = true;
-    Log.Warning("[SHUTDOWN] Ctrl+C 감지, 종료 중...");
-    cts.Cancel();
-};
+    public static readonly string SERVER_IP = "localhost";
+    public static readonly int SERVER_PORT = 9500;
+    public static readonly string CONNECTION_KEY = "test";
+    public static readonly int CLIENT_COUNT = 100;
 
-var service = new DummyClientService(CLIENT_COUNT, SERVER_IP, SERVER_PORT, CONNECTION_KEY, 100);
+    private static async Task Main(string[] args)
+    {
+        Log.Logger = new LoggerConfiguration().WriteTo.Console().CreateLogger();
 
-await service.RunAsync(cts.Token);
+        CancellationTokenSource cts = new CancellationTokenSource();
+        Console.CancelKeyPress += (_, e) =>
+        {
+            e.Cancel = true;
+            Log.Warning("[SHUTDOWN] Ctrl+C 감지, 종료 중...");
+            cts.Cancel();
+        };
 
-service.PrintStats();
-service.Stop();
+        DummyClientService service = new DummyClientService(CLIENT_COUNT, SERVER_IP, SERVER_PORT, CONNECTION_KEY, 100);
+        service.OnAllDisconnected += async () =>
+        {
+            Log.Warning("[SHUTDOWN] 종료 이벤트 발생, 종료 중...");
+            await cts.CancelAsync();
+        };
 
-Log.CloseAndFlush();
+        await service.RunAsync(cts.Token);
+
+        service.PrintStats();
+        service.Stop();
+
+        await Log.CloseAndFlushAsync();
+    }
+}
diff --git a/MMOTestServer/MMOserver/MMOserver.csproj b/MMOTestServer/MMOserver/MMOserver.csproj
index 4fde807..ddb6123 100644
--- a/MMOTestServer/MMOserver/MMOserver.csproj
+++ b/MMOTestServer/MMOserver/MMOserver.csproj
@@ -6,6 +6,7 @@
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
+        <LangVersion>13</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>
diff --git a/MMOTestServer/MMOserver/Packet/PacketBody.cs b/MMOTestServer/MMOserver/Packet/PacketBody.cs
index a3fbcc1..6cc4cac 100644
--- a/MMOTestServer/MMOserver/Packet/PacketBody.cs
+++ b/MMOTestServer/MMOserver/Packet/PacketBody.cs
@@ -1,6 +1,8 @@
+#pragma warning disable CS8618
+
 using ProtoBuf;
 
-namespace ClientTester.Packet;
+namespace MMOserver.Packet;
 
 // ============================================================
 // 공통 타입
diff --git a/MMOTestServer/MMOserver/Packet/PacketHeader.cs b/MMOTestServer/MMOserver/Packet/PacketHeader.cs
index b95aa68..f0c927c 100644
--- a/MMOTestServer/MMOserver/Packet/PacketHeader.cs
+++ b/MMOTestServer/MMOserver/Packet/PacketHeader.cs
@@ -1,55 +1,55 @@
-namespace ClientTester.Packet;
+namespace MMOserver.Packet;
 
-public enum PacketCode
+public enum PacketCode : short
 {
     NONE,
     // 초기 클라이언트 시작시 jwt토큰 받아옴
     RECV_TOKEN,
     // jwt토큰 검증후 게임에 들어갈지 말지 (내 데이터도 전송)
     LOAD_GAME,
-    
+
     // 마을(로비)진입시 모든 데이터 로드
     INTO_LOBBY,
-    
+
     // 로비 나가기
     EXIT_LOBBY,
-    
+
     // 인스턴스 던전 입장
     INTO_INSTANCE,
-    
+
     // 결과 보상
     REWARD_INSTANCE,
-    
+
     // 보스전 (시작, 종료)
     UPDATE_BOSS,
-    
+
     // 인스턴스 던전 퇴장
     EXIT_INSTANCE,
-    
+
     // 파티 (생성, 삭제)
     UPDATE_PARTY,
-    
+
     // 파티 유저 업데이트(추가 삭제)
     UPDATE_USER_PARTY,
-    
+
     // 플레이어 위치, 방향
     TRANSFORM_PLAYER,
-    
+
     // 플레이어 행동 업데이트
     ACTION_PLAYER,
-    
+
     // 플레이어 스테이트 업데이트
     STATE_PLAYER,
-    
+
     // NPC 위치, 방향
     TRANSFORM_NPC,
-    
+
     // NPC 행동 업데이트
     ACTION_NPC,
-    
+
     // NPC 스테이트 업데이트
     STATE_NPC,
-    
+
     // 데미지 UI 전달
     DAMAGE
 }
@@ -58,4 +58,4 @@ public class PacketHeader
 {
     public PacketCode Code;
     public int BodyLength;
-}
\ No newline at end of file
+}
diff --git a/MMOTestServer/MMOserver/Program.cs b/MMOTestServer/MMOserver/Program.cs
index 261bbe4..54c3062 100644
--- a/MMOTestServer/MMOserver/Program.cs
+++ b/MMOTestServer/MMOserver/Program.cs
@@ -1,6 +1,8 @@
 using MMOserver.Game;
 using Serilog;
 
+namespace MMOserver;
+
 class Program
 {
     private static void Main()
diff --git a/MMOTestServer/ServerLib/Packet/PacketSerializer.cs b/MMOTestServer/ServerLib/Packet/PacketSerializer.cs
index 1feebbb..9f9cb3f 100644
--- a/MMOTestServer/ServerLib/Packet/PacketSerializer.cs
+++ b/MMOTestServer/ServerLib/Packet/PacketSerializer.cs
@@ -1,3 +1,5 @@
+using System;
+using System.IO;
 using ProtoBuf;
 using Serilog;
 
diff --git a/MMOTestServer/ServerLib/ServerLib.csproj b/MMOTestServer/ServerLib/ServerLib.csproj
index 38c79cd..1da3505 100644
--- a/MMOTestServer/ServerLib/ServerLib.csproj
+++ b/MMOTestServer/ServerLib/ServerLib.csproj
@@ -4,6 +4,7 @@
         <TargetFramework>net9.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
+        <LangVersion>13</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>
diff --git a/MMOTestServer/ServerLib/Service/ServerBase.cs b/MMOTestServer/ServerLib/Service/ServerBase.cs
index 81bcdc1..95885b1 100644
--- a/MMOTestServer/ServerLib/Service/ServerBase.cs
+++ b/MMOTestServer/ServerLib/Service/ServerBase.cs
@@ -1,5 +1,8 @@
+using System;
+using System.Collections.Generic;
 using System.Net;
 using System.Net.Sockets;
+using System.Threading;
 using LiteNetLib;
 using LiteNetLib.Utils;
 using Serilog;
@@ -122,6 +125,13 @@ public abstract class ServerBase : INetEventListener
         {
             (ushort type, ushort size, byte[] payload) = PacketSerializer.Deserialize(data);
 
+            // 0이라면 에코 서버 테스트용 따로 처리
+            if (type == 0)
+            {
+                HandleEcho(peer, payload);
+                return;
+            }
+
             // Auth 패킷은 베이스에서 처리 (raw 8-byte long, protobuf 불필요)
             if (type == (ushort)PacketType.Auth)
             {
@@ -167,16 +177,33 @@ public abstract class ServerBase : INetEventListener
         }
     }
 
+    // Echo 서버 테스트
+
+    private void HandleEcho(NetPeer peer, byte[] payload)
+    {
+        // if (payload.Length < sizeof(long))
+        // {
+        //     Log.Warning("[Server] Echo 페이로드 크기 오류 PeerId={Id}", peer.Id);
+        //     peer.Disconnect();
+        //     return;
+        // }
+
+        // 세션에 넣지는 않는다.
+        NetDataReader reader = new NetDataReader(payload);
+        Log.Debug("[Echo] : addr={Addr}, str={Str}", peer.Address, reader.GetString());
+        SendTo(peer, payload);
+    }
+
     // ─── Auth 처리 (내부) ────────────────────────────────────────────────
 
     private void HandleAuth(NetPeer peer, byte[] payload)
     {
-        if (payload.Length < sizeof(long))
-        {
-            Log.Warning("[Server] Auth 페이로드 크기 오류 PeerId={Id}", peer.Id);
-            peer.Disconnect();
-            return;
-        }
+        // if (payload.Length < sizeof(long))
+        // {
+        //     Log.Warning("[Server] Auth 페이로드 크기 오류 PeerId={Id}", peer.Id);
+        //     peer.Disconnect();
+        //     return;
+        // }
 
         long hashKey = BitConverter.ToInt64(payload, 0);
 
diff --git a/MMOTestServer/ServerLib/Service/SessionManager.cs b/MMOTestServer/ServerLib/Service/SessionManager.cs
index 49cb4a8..6b16bd8 100644
--- a/MMOTestServer/ServerLib/Service/SessionManager.cs
+++ b/MMOTestServer/ServerLib/Service/SessionManager.cs
@@ -1,4 +1,6 @@
-namespace ServerLib.Service;
+using System.Collections.Generic;
+
+namespace ServerLib.Service;
 
 public class SessionManager
 {