Make the kernel_websocket_protocol flag reusable.

jupyter_server/services/kernels/connection/base.py

@@ -4,7 +4,7 @@
 
 from jupyter_client.session import Session
 from tornado.websocket import WebSocketHandler
-from traitlets import Float, Instance, default
+from traitlets import Float, Instance, Unicode, default
 from traitlets.config import LoggingConfigurable
 
 try:
@@ -14,6 +14,8 @@
 
 from jupyter_client.jsonutil import extract_dates
 
+from jupyter_server.transutils import _i18n
+
 from .abc import KernelWebsocketConnectionABC
 
 
@@ -110,6 +112,19 @@ def deserialize_msg_from_ws_v1(ws_msg):
 class BaseKernelWebsocketConnection(LoggingConfigurable):
     """A configurable base class for connecting Kernel WebSockets to ZMQ sockets."""
 
+    kernel_ws_protocol = Unicode(
+        None,
+        allow_none=True,
+        config=True,
+        help=_i18n(
+            "Preferred kernel message protocol over websocket to use (default: None). "
+            "If an empty string is passed, select the legacy protocol. If None, "
+            "the selected protocol will depend on what the front-end supports "
+            "(usually the most recent protocol supported by the back-end and the "
+            "front-end)."
+        ),
+    )
+
     @property
     def kernel_manager(self):
         """The kernel manager."""

jupyter_server/services/kernels/connection/channels.py

@@ -85,19 +85,6 @@ class ZMQChannelsWebsocketConnection(BaseKernelWebsocketConnection):
         ),
     )
 
-    kernel_ws_protocol = Unicode(
-        None,
-        allow_none=True,
-        config=True,
-        help=_i18n(
-            "Preferred kernel message protocol over websocket to use (default: None). "
-            "If an empty string is passed, select the legacy protocol. If None, "
-            "the selected protocol will depend on what the front-end supports "
-            "(usually the most recent protocol supported by the back-end and the "
-            "front-end)."
-        ),
-    )
-
     @property
     def write_message(self):
         """Alias to the websocket handler's write_message method."""