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/main.py

@@ -1,4 +1,5 @@
 import logging
+logging.basicConfig(level=logging.DEBUG)
 import time
 
 import zmq
@@ -25,6 +26,8 @@ def main_loop(context):
     for receiver in receivers:
         poller.register(receiver.socket, zmq.POLLIN)
 
+    logging.debug("Starting main loop.")
+
     while True:
         if state.exit_event.is_set(): break
         socks = dict(poller.poll(100))
@@ -36,7 +39,8 @@ def main_loop(context):
 
             message = receiver.socket.recv_json()
             response = receiver.handle_message(message)
-            receiver.socket.send_json(response)
+            if receiver.socket.getsockopt(zmq.TYPE) == zmq.REP:
+                receiver.socket.send_json(response)
 
             time_spent_ms = (time.time() - start_time) * 1000
             if time_spent_ms > 50:
@@ -51,7 +55,7 @@ def main():
     try:
         main_loop(context)
     except KeyboardInterrupt:
-        print("User interrupted.")
+        logging.info("User interrupted.")
     finally:
         state.deinitialize()
         context.term()