diff --git a/GLPIAPI.py b/GLPIAPI.py
index 18eb3c7..3bfdc01 100644
--- a/GLPIAPI.py
+++ b/GLPIAPI.py
@@ -32,6 +32,15 @@ class GLPIAPI:
                 "Session-Token": self.SessionToken,
                 "App-Token": self.AppToken
             }
+        else:
+            raise Exception(f"{result.status_code} - {result.json()[0]}")
+            
+    def CheckConnection(self):
+        sessionUri = f"{self.Server}/apirest.php/getFullSession/"
+        result = requests.get(sessionUri, headers=self.Headers)
+        if(result != 200 and result.json()[0] == 'ERROR_SESSION_TOKEN_INVALID'):
+            self.InitConnection()
+        return
     
     def GetComputers(self, deviceName=None, serialNumber=None, user=None, imei=None, airwatchDevice=None):
         '''
@@ -45,6 +54,7 @@ class GLPIAPI:
         
         Return a tuple with item id, item data and item count.
         '''
+        self.CheckConnection()
         searchAll = False
         if(deviceName != None):
             # Recherche en fonction du nom de l'appareil
@@ -115,6 +125,7 @@ class GLPIAPI:
         Return a tuple with item id (in a list if there are more than 1), item data (in a list of dict items) and item count (int).
         If the query does not succeed it will return a tuple with the http status code instead of item data (e.g. None, 400, 0).
         '''
+        self.CheckConnection()
         searchAll = False
         if(fieldName != None and fieldValue != None):
             fieldId = list(self.GetSearchOptions(itemType, fieldName))[0]
@@ -170,6 +181,7 @@ class GLPIAPI:
         return self.GetItems("User", fieldName, fieldValue)
         
     def GetSearchOptions(self, itemType, fieldName=None):
+        self.CheckConnection()
         queryUri = f"{self.Server}/apirest.php/listSearchOptions/{itemType}"
         searchOptions = requests.get(queryUri, headers=self.Headers)
         if(searchOptions.status_code == 200):
@@ -182,6 +194,7 @@ class GLPIAPI:
         return searchOptions.status_code
         
     def UploadFile(self, file, path):
+        self.CheckConnection()
         manifest = {
             "input": {
                 "name": file,
@@ -200,6 +213,7 @@ class GLPIAPI:
         return requests.post(self.Server+"/apirest.php/Document/", headers=headers, data=data, files=files)
     
     def SetDocumentToItem(self, itemID, itemType, documentID):
+        self.CheckConnection()
         body = { 
             "input": {
                 "documents_id": documentID,
@@ -210,6 +224,7 @@ class GLPIAPI:
         return requests.post(self.Server+"/apirest.php/Document/"+str(documentID)+"/Document_Item", headers=self.Headers, json=body)
 
     def UpdateInventory(self, inventory):
+        self.CheckConnection()
         headers = {
             "Content-Type":"Application/x-compress",
             "user-agent":self.UserAgent
@@ -225,6 +240,7 @@ class GLPIAPI:
             ...
            }
         '''
+        self.CheckConnection()
         body = {
             "input" : {
                 "id" : itemId,
@@ -236,7 +252,7 @@ class GLPIAPI:
         return requests.put(uri, headers=self.Headers, json=body)
     
     def UpdateSerialNumber(self, deviceid, serialnumber):
-    
+        self.CheckConnection()
         body = {
             "input" : {
                 "id" : deviceid,
@@ -247,7 +263,7 @@ class GLPIAPI:
         return requests.put(uri, headers=self.Headers, json=body)
     
     def UpdateItemUser(self, itemID, itemType, username):
-    
+        self.CheckConnection()
         body = {
             "input" : {
                 "id" : itemID,
@@ -262,6 +278,7 @@ class GLPIAPI:
            - containerName is block label name
            - containerID is block id
         '''
+        self.CheckConnection()
         uri = f"{self.Server}/apirest.php/PluginFields{itemType}{containerName}"
         searchURI = f"{self.Server}/apirest.php/PluginFields{itemType}{containerName}?range=0-999999999"
         result = requests.get(searchURI, headers=self.Headers)