Fix bobjacobsen#92: Generate Node ID (prevent alias reservation loop when two python-openlcb instances are running).

Poikilos · Poikilos · commit f6dd549bf727 · 2026-02-25T16:41:57.000-05:00
diff --git a/examples/examples_settings.py b/examples/examples_settings.py
@@ -9,6 +9,7 @@
 import sys
 
 from logging import getLogger
+
 if __name__ == "__main__":
     logger = getLogger(__file__)
 else:
@@ -26,10 +27,18 @@
         .format(repr(REPO_DIR)))
 CONFIGS_DIR = os.path.dirname(os.path.realpath(__file__))
 
+from openlcb.conventions import generate_node_id_str  # noqa: E402
+
+range_prefix = "05.01.01"  # 05.01.01 is *only* for Bob Jacobsen's
+#   python-openlcb (or as otherwise assigned by OpenLCB Group which
+#   reserves 05.* range). See
+#   <https://registry.openlcb.org/uniqueidranges>.
+
 DEFAULT_SETTINGS = {
     "host": "192.168.16.212",
     "port": 12021,
-    "localNodeID": "05.01.01.01.03.01",   # Warning: *only for openlcb*:
+    # "localNodeID": "05.01.01.01.03.01",   # Warning: *only for openlcb*:
+    "localNodeID": generate_node_id_str(range_prefix),
     #   See localNodeID_comment in SETTINGS_COMMENTS.
     "farNodeID": "02.01.57.00.04.9C",  # Serialized if hardware:
     #   See farNodeID_comment in SETTINGS_COMMENTS.
@@ -256,6 +265,11 @@ def load(self, settings_path=None, required=False):
             try:
                 with open(settings_path, 'r') as stream:
                     self._meta = json.load(stream)
+                    if 'localNodeID' in self._meta:
+                        del self._meta['localNodeID']
+                        # ^ Make sure it is unique on each run
+                        #   (unless set via load_cli_args,
+                        #   which isn't recommended).
             except json.decoder.JSONDecodeError:
                 self._meta = copy.deepcopy(DEFAULT_SETTINGS)
                 no_ext, dot_ext = os.path.splitext(settings_path)
diff --git a/openlcb/canbus/canlink.py b/openlcb/canbus/canlink.py
@@ -573,7 +573,8 @@ def handleReceivedAMD(self, frame: CanFrame):
     def handleGlobalAME(self, frame: CanFrame):
         """If no data, clear all except self from maps
         even if not in Permitted state
-        (CAN Frame Transfer Standard, 6.2.3).
+        (CAN Frame Transfer Standard, 6.2.3
+        Alias Map Enquiry).
         """
         if frame.data:  # not global
             return
@@ -589,9 +590,10 @@ def handleGlobalAME(self, frame: CanFrame):
             #     pass  # concurrent modification
             if otherNodeID == self.localNodeID:
                 continue
-            del self.nodeIdToAlias[otherNodeID]
-            # except KeyError:
-            #     pass  # concurrent modification
+            try:
+                del self.nodeIdToAlias[otherNodeID]
+            except KeyError:
+                pass  # concurrent modification?
             # TODO: clear matching _send_frames??
 
     def handleReceivedAME(self, frame: CanFrame):
diff --git a/openlcb/conventions.py b/openlcb/conventions.py
@@ -175,9 +175,9 @@ def generate_node_id_str(id_range_prefix) -> str:
     Args:
         id_range_prefix (str): NodeID prefix in dotted hex notation
             (3 to 5. 3 at most recommended to make uniqueness more
-            likely) Warning: 05.01.01 is *only* for Bob Jacobsen's
+            likely) Warning: "05.01.01" is *only* for Bob Jacobsen's
             python-openlcb (or as otherwise assigned by OpenLCB Group
-            which reserves 05.* range) See
+            which reserves 05.* range). See
             <https://registry.openlcb.org/uniqueidranges>.
     Returns:
         str: Full 48-bit node ID in dotted hex string notation (Example:
diff --git a/openlcb/nodeid.py b/openlcb/nodeid.py
@@ -97,7 +97,7 @@ def generate_node_id(id_range_prefix):
         id_range_prefix (str): NodeID prefix in dotted hex notation.
             Warning: 05.01.01 is *only* for Bob Jacobsen's
             python-openlcb (or as otherwise assigned by OpenLCB Group
-            which reserves 05.* range) See
+            which reserves 05.* range). See
             <https://registry.openlcb.org/uniqueidranges>.
     Returns:
         NodeID: A NodeID that is unique (very likely...).
