The protocol change moving control messages from PUB/SUB to ROUTER/DEALER broke the Python client, which only polled the SUB socket. The client couldn't receive RPC, Network Variables, or Device ID mappings, but tests passed due to missing assertions.

Changes

Python Client (client.py)

• Poll both DEALER and SUB sockets in receive loop
• DEALER receives control messages (RPC, NV, Device ID mappings) from ROUTER
• SUB receives transform broadcasts from PUB
• Auto-send stealth handshake on start to register with server

Binary Serializer (binary_serializer.py)

• Fixed device ID mapping deserializer to skip 3-byte version header
• Pre-existing bug exposed by protocol change

Example

Before (broken):

# Only SUB socket polled
poller = zmq.Poller()
if self._sub_socket:
    poller.register(self._sub_socket, zmq.POLLIN)

After (fixed):

# Both sockets polled
poller = zmq.Poller()
if self._sub_socket:
    poller.register(self._sub_socket, zmq.POLLIN)
if self._dealer_socket:
    poller.register(self._dealer_socket, zmq.POLLIN)  # Control messages

# Handle DEALER messages
if self._dealer_socket in socks:
    message_parts = self._dealer_socket.recv_multipart()
    self._process_message(message_parts[1])  # [room_id, payload]

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