diff --git a/src/pubsub/pubsub/pubsub_library_v3.py b/src/pubsub/pubsub/pubsub_library_v3.py
index 519e108..c235bcc 100644
--- a/src/pubsub/pubsub/pubsub_library_v3.py
+++ b/src/pubsub/pubsub/pubsub_library_v3.py
@@ -111,16 +111,41 @@ class MinimalSubscriber(Node):
 #******************************************************************************#
 
 class MinimalServiceProvider(Node):
-    def __init__(self, NODE_NAME, SRV_NAME, SRV_TYPE):
+    """ Minimal Service Provider Class
+    Inputs:
+    * NODE_NAME: string
+    * SRV_NAME: string
+    * SRV_TYPE: service type class
+    * srv_callback_fct: service callback function
+
+    srv_callback_fct - Inputs:
+    * request: class of type srv request
+    * response: class of type srv response
+
+    Return:
+    * response: class of type srv response
+    """
+
+
+    def __init__(self, NODE_NAME, SRV_NAME, SRV_TYPE, srv_callback_fct=None):
         self.NODE_NAME = NODE_NAME
         self.SRV_NAME = SRV_NAME
         self.SRV_TYPE = SRV_TYPE
+        if srv_callback_fct == None:
+            self.srv_callback = self.std_srv_callback
+        else:
+            self.srv_callback = srv_callback_fct
         # Init above laying class "Node" 
         super().__init__(self.NODE_NAME)
-        print("\tStarting Service Host:\t%s"%(self.SRV_NAME))
-        self.srv_host = self.create_service(self.SRV_TYPE, self.SRV_NAME, self.service_callback)
+        print("\tStarting Service as Host:\t%s"%(self.SRV_NAME))
+        #self.srv_host = self.create_service(self.SRV_TYPE, self.SRV_NAME, self.service_callback)
+        self.srv_host = self.create_service(self.SRV_TYPE, self.SRV_NAME, self.srv_callback)
 
-    def service_callback(self, request, response):
+
+
+
+    #def service_callback(self, request, response):
+    def std_srv_callback(self, request, response):
         """
         * request: first half of srv-file
         * response: second half of srv-file
@@ -134,7 +159,6 @@ class MinimalServiceProvider(Node):
         response = self.user_defined(request, response) # Function defined below
         return response
 
-
     # Insert your callback code here
     def user_defined(self, request, response):
         """ Write your user defined code here which will be run at every service call