diff --git a/Client/Client.cs b/Client/Client.cs
index e65204f..ca6b53f 100644
--- a/Client/Client.cs
+++ b/Client/Client.cs
@@ -15,6 +15,7 @@ namespace Client
         private byte[] totalBuffer = new byte[1024];
         private int totalBufferReceived = 0;
         private EngineConnection engineConnection;
+        private bool sessionRunning = false;
 
 
         public Client() : this("localhost", 5555)
@@ -40,7 +41,7 @@ namespace Client
         private void OnConnect(IAsyncResult ar)
         {
             this.client.EndConnect(ar);
-            Console.WriteLine("Verbonden!");
+            Console.WriteLine("TCP client Verbonden!");
 
 
             this.stream = this.client.GetStream();
@@ -91,6 +92,16 @@ namespace Client
                                 tryLogin();
                             }
                             break;
+                        case DataParser.START_SESSION:
+                            this.sessionRunning = true;
+                            byte[] startSession = DataParser.getStartSessionJson();
+                            stream.BeginWrite(startSession, 0, startSession.Length, new AsyncCallback(OnWrite), null);
+                            break;
+                        case DataParser.STOP_SESSION:
+                            this.sessionRunning = false;
+                            byte[] stopSession = DataParser.getStopSessionJson();
+                            stream.BeginWrite(stopSession, 0, stopSession.Length, new AsyncCallback(OnWrite), null);
+                            break;
                         default:
                             Console.WriteLine($"Received json with identifier {identifier}:\n{Encoding.ASCII.GetString(payloadbytes)}");
                             break;
@@ -118,6 +129,10 @@ namespace Client
         //maybe move this to other place
         public void BPM(byte[] bytes)
         {
+            if (!sessionRunning)
+            {
+                return;
+            }
             if (bytes == null)
             {
                 throw new ArgumentNullException("no bytes");
@@ -128,6 +143,10 @@ namespace Client
 
         public void Bike(byte[] bytes)
         {
+            if (!sessionRunning)
+            {
+                return;
+            }
             if (bytes == null)
             {
                 throw new ArgumentNullException("no bytes");
diff --git a/Client/DataParser.cs b/Client/DataParser.cs
index c83b86a..fd1c7e8 100644
--- a/Client/DataParser.cs
+++ b/Client/DataParser.cs
@@ -3,6 +3,7 @@ using Newtonsoft.Json.Serialization;
 using System;
 using System.Globalization;
 using System.Linq;
+using System.Runtime.InteropServices.WindowsRuntime;
 using System.Text;
 
 namespace Client
@@ -10,7 +11,9 @@ namespace Client
     public class DataParser
     {
         public const string LOGIN = "LOGIN";
-        public const string LOGIN_RESPONSE = "LOGIN_RESPONSE";
+        public const string LOGIN_RESPONSE = "LOGIN RESPONSE";
+        public const string START_SESSION = "START SESSION";
+        public const string STOP_SESSION = "STOP SESSION";
         /// <summary>
         /// makes the json object with LOGIN identifier and username and password
         /// </summary>
@@ -161,6 +164,21 @@ namespace Client
             return getJsonMessage(Encoding.ASCII.GetBytes(message));
         }
 
+        public static byte[] getStartSessionJson()
+        {
+            return getJsonMessage(START_SESSION, null);
+        }
+
+        public static byte[] getStopSessionJson()
+        {
+            return getJsonMessage(STOP_SESSION, null);
+        }
+
+        public static byte[] getSetResistanceJson()
+        {
+            return null;
+        }
+
 
     }
 }
diff --git a/Server/Client.cs b/Server/Client.cs
index fc4baca..1b357be 100644
--- a/Server/Client.cs
+++ b/Server/Client.cs
@@ -105,7 +105,8 @@ namespace Server
                                 this.username = username;
                                 byte[] response = DataParser.getLoginResponse("OK");
                                 stream.BeginWrite(response, 0, response.Length, new AsyncCallback(OnWrite), null);
-                                this.saveData = new SaveData(Directory.GetCurrentDirectory() + "/" + username, sessionStart.ToString("yyyy-MM-dd HH-mm-ss"));
+                                byte[] startSession = DataParser.getStartSessionJson();
+                                stream.BeginWrite(startSession, 0, startSession.Length, new AsyncCallback(OnWrite), null);
                             }
                             else
                             {
@@ -119,6 +120,12 @@ namespace Server
                             stream.BeginWrite(response, 0, response.Length, new AsyncCallback(OnWrite), null);
                         }
                         break;
+                    case DataParser.START_SESSION:
+                        this.saveData = new SaveData(Directory.GetCurrentDirectory() + "/" + this.username + "/" + sessionStart.ToString("yyyy-MM-dd HH-mm-ss"));
+                        break;
+                    case DataParser.STOP_SESSION:
+                        this.saveData = null;
+                        break;
                     default:
                         Console.WriteLine($"Received json with identifier {identifier}:\n{Encoding.ASCII.GetString(payloadbytes)}");
                         break;
@@ -130,11 +137,11 @@ namespace Server
                 Console.WriteLine(BitConverter.ToString(payloadbytes));
                 if (payloadbytes.Length == 8)
                 {
-                    saveData.WriteDataRAWBike(payloadbytes);
+                    saveData?.WriteDataRAWBike(payloadbytes);
                 }
                 else if (payloadbytes.Length == 2)
                 {
-                    saveData.WriteDataRAWBPM(payloadbytes);
+                    saveData?.WriteDataRAWBPM(payloadbytes);
                 }
                 else
                 {
diff --git a/Server/SaveData.cs b/Server/SaveData.cs
index 4163471..15fd0d4 100644
--- a/Server/SaveData.cs
+++ b/Server/SaveData.cs
@@ -8,11 +8,9 @@ namespace Server
     class SaveData
     {
         private string path;
-        private string filename;
-        public SaveData(string path, string filename)
+        public SaveData(string path)
         {
             this.path = path;
-            this.filename = filename;
             if (!Directory.Exists(path))
             {
                 Directory.CreateDirectory(path);
@@ -25,7 +23,7 @@ namespace Server
 
         public void WriteDataJSON(string data)
         {
-            using (StreamWriter sw = File.AppendText(this.path + "/json" + filename + ".txt"))
+            using (StreamWriter sw = File.AppendText(this.path + "/json" + ".txt"))
             {
                 sw.WriteLine(data);
             }
@@ -37,7 +35,7 @@ namespace Server
             {
                 throw new ArgumentException("data should have length of 2");
             }
-            WriteRawData(data, this.path + "/rawBPM" + filename + ".bin");
+            WriteRawData(data, this.path + "/rawBPM" + ".bin");
         }
 
         public void WriteDataRAWBike(byte[] data)
@@ -46,7 +44,7 @@ namespace Server
             {
                 throw new ArgumentException("data should have length of 8");
             }
-            WriteRawData(data, this.path + "/rawBike" + filename + ".bin");
+            WriteRawData(data, this.path + "/rawBike" + ".bin");
         }
 
         private void WriteRawData(byte[] data, string fileLocation)