diff --git a/engine.py b/engine.py
index be87120..1d0a044 100644
--- a/engine.py
+++ b/engine.py
@@ -1,7 +1,7 @@
 from datetime import datetime
 
 
-class Log():
+class Log:
     def __init__(self, settings=None):
         if settings is None:
             settings = {"save_error": True, "print_error": True, "save_warning": True, "print_warning": True,
diff --git a/filesystem.json b/filesystem.json
new file mode 100644
index 0000000..bfb59b2
--- /dev/null
+++ b/filesystem.json
@@ -0,0 +1,22 @@
+{
+  "ID": 0,
+    "location": "izba",
+    "descrpition": {
+      "title": "legionrpi",
+      "description_s": "krátky popis, ktorý bude zobrazený iba v náhladovom okne",
+      "description_l": "dlhší popis zariadenia, ktorý bude zobrazený po otvorení",
+      "photo_s": "mala_fotka.png",
+      "photo_b": "velka fotka.png"
+    },
+    "files": [
+      {
+        "name": "test",
+        "format": ".jpg",
+        "description": "toto je jpg test file"
+      }, {
+        "name": "test2",
+        "format": ".txt",
+        "description": "toto je txt test file"
+      }
+    ]
+}
\ No newline at end of file
diff --git a/log.txt b/log.txt
index e69de29..66ecc27 100644
--- a/log.txt
+++ b/log.txt
@@ -0,0 +1,3 @@
+
+2021-03-15 10:13:26.660898 -> Warning: 192.168.1.232 disconnected/is not available
+2021-03-15 11:23:33.589998 -> Warning: 192.168.1.231 disconnected/is not available
\ No newline at end of file
diff --git a/main.py b/main.py
index e9b9a59..9c6f979 100644
--- a/main.py
+++ b/main.py
@@ -7,20 +7,22 @@ import time
 import json
 import os
 import threading
+import hashlib
 
-with open("settings.json", "r") as f:   #loading settings
+with open("settings.json", "r") as f:  # loading settings
     settings = json.load(f)
 
 IP = settings["IP"]
 ID = settings["ID"]
 location = settings["location"]
 
-app = FastAPI()                     #init of FastAPI
+app = FastAPI()  # init of FastAPI
 log = engine.Log(settings["log"])  # init of LOG
 offline = []
 
 time_to_heartbeat = settings["time_to_heartbeat"]  # Raspberry will be requesting heartbeat every __ seconds
-time_to_heartbeat_offline = settings["time_to_heartbeat_offline"]  # Raspberry will be requesting heartbeat every __ seconds from offline rpi
+time_to_heartbeat_offline = settings[
+    "time_to_heartbeat_offline"]  # Raspberry will be requesting heartbeat every __ seconds from offline rpi
 
 # json variables
 filesystem = {  # Here will be files saved on this raspberry
@@ -45,7 +47,7 @@ heartbeat_table["last_heartbeat"].append(time_to_heartbeat)
 
 # Todo better "host" ID handeling
 
-class Server_table(BaseModel):  # table of content for heartbeat request
+class ServerTable(BaseModel):  # table of content for heartbeat request
     ID: list
     IP: list
     location: list
@@ -54,9 +56,10 @@ class Server_table(BaseModel):  # table of content for heartbeat request
 
 
 @app.post("/heartbeat")
-def heartbeat(s_table: Server_table, request: Request):
+def heartbeat(s_table: ServerTable, request: Request):
     log.message(f"server requested heartbeat {request.client.host}:{request.client.port}")
     log.debug(f"Recieved server table: {s_table}")
+
     try:
         for position, server_id in enumerate(s_table.ID):
             if server_id in heartbeat_table["ID"]:
@@ -78,9 +81,11 @@ def heartbeat(s_table: Server_table, request: Request):
                 heartbeat_table["last_heartbeat"].append(s_table.last_heartbeat[position])
     except Exception as error:
         log.error(f"heartbeat > {error}")
+
     if heartbeat_table["ID"][heartbeat_table["IP"].index(request.client.host)] in offline:
         offline.remove(heartbeat_table["ID"][heartbeat_table["IP"].index(request.client.host)])
         log.message(f"{request.client.host} gone online")
+
     return heartbeat_table, {"ID": ID, "file_system": filesystem, "location": location}
 
 
@@ -93,23 +98,28 @@ def get_sensors(request: Request):
 
 @app.get("/files/{IDx}/{file}")
 def get_file(IDx: int, file: str):
+    server_ip = heartbeat_table["IP"][heartbeat_table["ID"].index(IDx)]
     if IDx == ID:
         return FileResponse(f"files/{file}")
     elif IDx in heartbeat_table["ID"]:
-        r = requests.get(
-            f"""http://{heartbeat_table["IP"][heartbeat_table["ID"].index(IDx)]}:8000/files/{IDx}/{file}""")
-        r.encoding = "utf-8"
         if os.path.isdir(f"cache/{IDx}"):
             if os.path.isfile(f"cache/{IDx}/{file}"):
-                pass
-                # Todo cache time to live/compare files on server and cache with not resource heavy function
-            else:
-                with open(f"cache/{IDx}/{file}", "wb") as save:
-                    save.write(bytes(r.content))
+                with open(f"cache/{IDx}/{file}", "rb") as compared_file:
+                    m = hashlib.md5()
+                    for line in compared_file:
+                        m.update(line)
+                rr = requests.get(f"""http://{server_ip}:8000/compare/{file}""")
+                if rr.text.strip('"') != str(m.hexdigest()):
+                    log.message(f"{file} on server {server_ip} is changed.")
+                else:
+                    log.debug(f"returning cached file cache/{IDx}{file}")
+                    return FileResponse(f"cache/{IDx}/{file}")
         else:
             os.mkdir(f"cache/{IDx}")
-            with open(f"cache/{IDx}/{file}", "wb") as save:
-                save.write(bytes(r.content))
+        log.message(f"downloading {file} from {server_ip}")
+        r = requests.get(f"http://{server_ip}:8000/files/{IDx}/{file}")
+        with open(f"cache/{IDx}/{file}", "wb") as save:
+            save.write(bytes(r.content))
         return FileResponse(f"cache/{IDx}/{file}")
 
 
@@ -119,6 +129,20 @@ def update_sensors():
     # Todo Make option to upload "live data" manually to rpi
 
 
+@app.get("/compare/{file}")
+def comparision(file: str):
+    with open(f"files/{file}", "rb") as compared_file:
+        m = hashlib.md5()
+        for line in compared_file:
+            m.update(line)
+    return m.hexdigest()
+
+
+@app.get("/devices_list")
+def get_devices_list():
+    return heartbeat_table
+
+
 def send_heartbeat(ip, id):
     global heartbeat_table
     log.message(f"""sending heartbeat to {ip}({"offline" if id in offline else "online"})""")
@@ -153,4 +177,7 @@ thread_1 = threading.Thread(target=mainloop, daemon=True)
 thread_1.start()
 
 # Todo in next release: disconnect offline client after set time
-# Todo better formating code + comments
\ No newline at end of file
+# Todo send to mobile
+# Todo new filesystem handeling
+# Todo implement update system
+# Todo settings for easy adding/editing files/id/text
\ No newline at end of file
diff --git a/settings.json b/settings.json
index e670bca..989602e 100644
--- a/settings.json
+++ b/settings.json
@@ -12,12 +12,5 @@
     "save_message": false,
     "print_message": true,
     "enable_debug": false
-  },
-  "heartbeat_table": {
-    "ID": [],
-    "IP": [],
-    "location": [],
-    "file_system": [],
-    "last_heartbeat": []
+  }
 }
-}
\ No newline at end of file
diff --git a/version.json b/version.json
new file mode 100644
index 0000000..63f5b53
--- /dev/null
+++ b/version.json
@@ -0,0 +1,4 @@
+{
+  "version": "0.1",
+  "type": "Alpha"
+}
\ No newline at end of file