Starting a fPolicy server using python

Aman-Chaurasia — Wed, 23 Jul 2025 13:25:46 GMT

I want to set up a fpolicy server, which I can connect to from ontap.
I have tried setting up one using python as shown below. But I am getting below error when ontap tries to connect to it.
Error -

Reason for FPolicy Server Disconnection: FPolicy server sent message in which didn't had correct length format marker.

FPolicy Server using Python :-

import socket import struct import xml.etree.ElementTree as ET def start_fpolicy_server(host, port): server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_socket.bind((host, port)) server_socket.listen(5) print(f"FPolicy listen-only server started on {host}:{port}") while True: client_socket, addr = server_socket.accept() print(f"Connection from {addr}") handle_client(client_socket) def handle_client(client_socket): try: while True: data = client_socket.recv(4096) if not data: break print(f"Received data: {data}") # Process the handshake request response = process_handshake_request(data) if response: print(f"Sending response: {response}") client_socket.sendall(response) finally: client_socket.close() def process_handshake_request(data): try: # Print the raw data for debugging print("Raw data:", data) # Split the data to separate the header and the body parts = data.split(b'\n\n', 1) if len(parts) != 2: raise ValueError("Invalid data format: missing header or body") header, body = parts # Print the header and body for debugging print("Header:", header) print("Body:", body) # Decode the XML body and remove the null character body_str = body.decode('utf-8').rstrip('\x00') # Print the decoded body for debugging print("Decoded Body:", body_str) # Parse the XML body root = ET.fromstring(body_str) if root.tag == 'Handshake': session_id = root.find('SessionId').text vs_uuid = root.find('VsUUID').text policy_name = root.find('PolicyName').text # Construct the handshake response response_body = f'''<?xml version="1.0"?> <Header> <NotfType>NEGO_RESP</NotfType> <ContentLen>0</ContentLen> <DataFormat>XML</DataFormat> </Header> <?xml version="1.0"?> <HandshakeResp> <SessionId>{session_id}</SessionId> <VsUUID>{vs_uuid}</VsUUID> <PolicyName>{policy_name}</PolicyName> <ProtVersion>3.0</ProtVersion> </HandshakeResp>''' # Encode the response body response_body_bytes = response_body.encode('utf-8') # Calculate the length of the response body response_length = len(response_body_bytes) #+ 4 # Include the length of the length prefix itself # Construct the length prefix (4 bytes, network byte order) length_prefix = struct.pack('!I', response_length) # Combine the length prefix and the response body response = length_prefix + response_body_bytes return response except Exception as e: print(f"Error processing handshake request: {e}") return None if __name__ == "__main__": start_fpolicy_server("0.0.0.0", 9000)

topic Starting a fPolicy server using python in ONTAP Discussions

Starting a fPolicy server using python