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/socket_base.py

@@ -1,5 +1,9 @@
 from abc import ABCMeta
 
+import zmq
+
+from robot_interface.utils import zmq_socket_type_int_to_str, zmq_socket_type_complement
+
 
 class SocketBase(object):
     __metaclass__ = ABCMeta
@@ -7,15 +11,21 @@ class SocketBase(object):
     name = None
     socket = None
 
-    def __init__(self, name):
+    def __init__(self, name, data_type):
         """
         :param name: The name of the endpoint.
         :type name: str
+
+        :param data_type: The data type of the endpoint, e.g. "json", "binary", "text", etc.
+        :type data_type: str
         """
         self.name = name
-        self.socket = None
+        self.data_type = data_type
+        self.port = None  # Set later by `create_socket`
+        self.socket = None  # Set later by `create_socket`
+        self.bound = None  # Set later by `create_socket`
 
-    def create_socket(self, zmq_context, socket_type, port):
+    def create_socket(self, zmq_context, socket_type, port, bind=True):
         """
         Create a ZeroMQ socket.
 
@@ -27,12 +37,35 @@ class SocketBase(object):
 
         :param port: The port to use.
         :type port: int
+
+        :param bind: Whether to bind the socket or connect to it.
+        :type bind: bool
         """
+        self.port = port
         self.socket = zmq_context.socket(socket_type)
-        self.socket.connect("tcp://localhost:{}".format(port))
+        self.bound = bind
+        if bind:
+            self.socket.bind("tcp://*:{}".format(port))
+        else:
+            self.socket.connect("tcp://localhost:{}".format(port))
 
     def close(self):
         """Close the ZeroMQ socket."""
         if not self.socket: return
         self.socket.close()
         self.socket = None
+
+    def endpoint_description(self):
+        """
+        Description of the endpoint. Used for negotiation.
+
+        :return: A dictionary with the following keys: name, port, pattern, data_type. See https://utrechtuniversity.youtrack.cloud/articles/N25B-A-14/RI-CB-Communication#negotiation
+        :rtype: dict
+        """
+        return {
+            "name": self.name,
+            "port": self.port,
+            "pattern": zmq_socket_type_int_to_str[zmq_socket_type_complement[self.socket.getsockopt(zmq.TYPE)]],
+            "data_type": self.data_type,
+            "bind": not self.bound
+        }