feat: implement negotiation

By implementing SocketBase and adding the socket to the state, the negotiation will automatically give the right endpoints.

ref: N25B-168

src/robot_interface/endpoints/main_receiver.py

@@ -1,6 +1,7 @@
 import zmq
 
 from robot_interface.endpoints.receiver_base import ReceiverBase
+from robot_interface.state import state
 
 
 class MainReceiver(ReceiverBase):
@@ -14,14 +15,20 @@ class MainReceiver(ReceiverBase):
         :param port: The port to use.
         :type port: int
         """
-        super(MainReceiver, self).__init__("main")
-        self.create_socket(zmq_context, zmq.REP, port)
+        super(MainReceiver, self).__init__("main", "json")
+        self.create_socket(zmq_context, zmq.REP, port, bind=False)
 
     @staticmethod
     def _handle_ping(message):
         """A simple ping endpoint. Returns the provided data."""
         return {"endpoint": "ping", "data": message.get("data")}
 
+    @staticmethod
+    def _handle_port_negotiation(message):
+        endpoints = [socket.endpoint_description() for socket in state.sockets]
+
+        return {"endpoint": "negotiation/ports", "data": endpoints}
+
     @staticmethod
     def _handle_negotiation(message):
         """
@@ -33,7 +40,11 @@ class MainReceiver(ReceiverBase):
         :return: A response dictionary with a 'ports' key containing a list of ports and their function.
         :rtype: dict[str, list[dict]]
         """
-        # TODO: .../error on all endpoints?
+        # In the future, the sender could send information like the robot's IP address, etc.
+
+        if message["endpoint"] == "negotiation/ports":
+            return MainReceiver._handle_port_negotiation(message)
+
         return {"endpoint": "negotiation/error", "data": "The requested endpoint is not implemented."}
 
     def handle_message(self, message):
@@ -42,7 +53,7 @@ class MainReceiver(ReceiverBase):
 
         if message["endpoint"] == "ping":
             return self._handle_ping(message)
-        elif message["endpoint"] == "negotiation":
+        elif message["endpoint"].startswith("negotiation"):
             return self._handle_negotiation(message)
 
         return {"endpoint": "error", "data": "The requested endpoint is not supported."}