Fix WebSocket handshake failure for chargers missing Connection: Upgrade header

custom_components/ocpp/api.py

@@ -16,6 +16,7 @@
 import homeassistant.helpers.config_validation as cv
 import voluptuous as vol
 from websockets import Subprotocol, NegotiationError
+from websockets.http11 import Request, Response
 import websockets.server
 from websockets.asyncio.server import ServerConnection
 
@@ -37,6 +38,33 @@
 _LOGGER: logging.Logger = logging.getLogger(__package__)
 # Uncomment these when Debugging
 # logging.getLogger("asyncio").setLevel(logging.DEBUG)
+
+
+async def _fix_missing_connection_header(
+    connection: ServerConnection, request: Request
+) -> Response | None:
+    """Work around charger firmware that omits the Connection: Upgrade header.
+
+    Some charger firmware (e.g. Autel MaxiCharger US AC LW10-N14,
+    firmware v1.38.00/v1.22.00) omits the required Connection: Upgrade
+    header from the WebSocket opening handshake.
+
+    websockets 14+ strictly validates this header and raises
+    InvalidUpgrade when it is absent, preventing the charger from
+    ever connecting.  We inject the header before the library validates
+    it so that the handshake can proceed normally.
+    """
+    if not request.headers.get_all("Connection"):
+        _LOGGER.warning(
+            "Charger at %s sent a WebSocket upgrade request without the "
+            "required 'Connection: Upgrade' header. Injecting header as "
+            "a workaround — consider updating the charger firmware.",
+            connection.remote_address,
+        )
+        request.headers["Connection"] = "upgrade"
+    return None
+
+
 # logging.getLogger("websockets").setLevel(logging.DEBUG)
 
 UFW_SERVICE_DATA_SCHEMA = vol.Schema(
@@ -184,6 +212,7 @@ async def create(hass: HomeAssistant, entry: ConfigEntry):
             self.on_connect,
             self.settings.host,
             self.settings.port,
+            process_request=_fix_missing_connection_header,
             select_subprotocol=self.select_subprotocol,
             subprotocols=self.subprotocols,
             ping_interval=None,  # ping interval is not used here, because we send pings mamually in ChargePoint.monitor_connection()

tests/test_api_paths.py

@@ -10,7 +10,7 @@
 from homeassistant.exceptions import HomeAssistantError
 from websockets import NegotiationError
 
-from custom_components.ocpp.api import CentralSystem
+from custom_components.ocpp.api import CentralSystem, _fix_missing_connection_header
 from custom_components.ocpp.const import DOMAIN
 from custom_components.ocpp.enums import (
     HAChargerServices as csvcs,
@@ -412,3 +412,40 @@ def test_del_metric_variants(hass):
 
     # --- Case C: unknown cpid -> returns None, no exception
     assert cs.del_metric("unknown_cpid", "Voltage") is None
+
+
+@pytest.mark.asyncio
+async def test_fix_missing_connection_header_injects_when_absent(caplog):
+    """Header is injected and warning logged when Connection header is missing."""
+    import logging
+    from websockets.datastructures import Headers
+
+    headers = Headers()  # empty — no Connection header
+    request = SimpleNamespace(headers=headers)
+    connection = SimpleNamespace(remote_address=("192.168.1.100", 9000))
+
+    with caplog.at_level(logging.WARNING):
+        result = await _fix_missing_connection_header(connection, request)
+
+    assert result is None
+    assert request.headers.get("Connection") == "upgrade"
+    assert "Connection: Upgrade" in caplog.text
+
+
+@pytest.mark.asyncio
+async def test_fix_missing_connection_header_leaves_existing_intact(caplog):
+    """Existing Connection header is not overwritten and no warning is logged."""
+    import logging
+    from websockets.datastructures import Headers
+
+    headers = Headers()
+    headers["Connection"] = "Upgrade"
+    request = SimpleNamespace(headers=headers)
+    connection = SimpleNamespace(remote_address=("192.168.1.100", 9000))
+
+    with caplog.at_level(logging.WARNING):
+        result = await _fix_missing_connection_header(connection, request)
+
+    assert result is None
+    assert request.headers.get("Connection") == "Upgrade"
+    assert not any(r.levelname == "WARNING" for r in caplog.records)