feat: basic implementation of standardized CB2RI communication API

Based on the N25B-A-14 article, this is a stub implementation of the RI2CB communication API. It implements the ping endpoint and provides a stub for the negotiation endpoint.

ref: N25B-168

src/robot_interface/main.py

@@ -0,0 +1,67 @@
+import zmq
+
+
+def handle_ping(message):
+    """A simple ping endpoint. Returns the provided data."""
+    return {"endpoint": "ping", "data": message.get("data")}
+
+
+def handle_negotiation(message):
+    """
+    Handle a negotiation request. Will respond with ports that can be used to connect to the robot.
+
+    :param message: The negotiation request message.
+    :type message: dict
+
+    :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?
+    return {"endpoint": "negotiation/error", "data": "The requested endpoint is not implemented."}
+
+
+def route_request(message):
+    """
+    Handle a request message.
+
+    :param message: The request message.
+    :type message: dict
+
+    :return: A response message.
+    :rtype: dict
+    """
+    print("Received request: {}".format(message))
+
+    if "endpoint" not in message:
+        return {"endpoint": "error", "data": "No endpoint provided."}
+    if message["endpoint"] == "ping":
+        return handle_ping(message)
+    elif message["endpoint"] == "negotiation":
+        return handle_negotiation(message)
+
+    return {"endpoint": "error", "data": "The requested endpoint is not implemented."}
+
+
+def main_loop(socket):
+    while True:
+        request = socket.recv_json()
+        response = route_request(request)
+        socket.send_json(response)
+
+
+def main():
+    context = zmq.Context()
+    socket = context.socket(zmq.REP)
+    socket.connect("tcp://localhost:5555")
+
+    try:
+        main_loop(socket)
+    except KeyboardInterrupt:
+        print("User interrupted.")
+    finally:
+        socket.close()
+        context.term()
+
+
+if __name__ == "__main__":
+    main()