home-assistant/core · warning · ConfigEntryNotReady

Connection error from CalDAV server

Error message

Connection error from CalDAV server

What it means

ConfigEntryNotReady raised when client.principal() raises requests.ConnectionError — TCP-level failure to connect to the CalDAV URL (DNS failure, refused connection, unreachable host). HA schedules a retry with backoff.

Source

Thrown at homeassistant/components/caldav/__init__.py:51

        entry.data[CONF_URL],
        username=entry.data[CONF_USERNAME],
        password=entry.data[CONF_PASSWORD],
        ssl_verify_cert=entry.data[CONF_VERIFY_SSL],
        timeout=TIMEOUT,
    )
    try:
        await hass.async_add_executor_job(client.principal)
    except AuthorizationError as err:
        if err.reason == "Unauthorized":
            raise ConfigEntryAuthFailed("Credentials error from CalDAV server") from err
        # AuthorizationError can be raised if the url is incorrect or
        # on some other unexpected server response.
        _LOGGER.warning("Unexpected CalDAV server response: %s", err)
        return False
    except requests.Timeout as err:
        raise ConfigEntryNotReady("Timeout connecting to CalDAV server") from err
    except requests.ConnectionError as err:
        raise ConfigEntryNotReady("Connection error from CalDAV server") from err
    except DAVError as err:
        raise ConfigEntryNotReady("CalDAV client error") from err

    entry.runtime_data = client

    await hass.config_entries.async_forward_entry_setups(entry, PLATFORMS)

    return True


async def async_unload_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
    """Unload a config entry."""
    return await hass.config_entries.async_unload_platforms(entry, PLATFORMS)

View on GitHub (pinned to 58a3fdb3ea)

Solutions

1. Confirm the URL and port from the browser/curl on the same host running Home Assistant
2. Fix DNS or use an IP/resolvable name; ensure the CalDAV service is running
3. If using https, verify the certificate is trusted (see CONF_VERIFY_SSL setting in the entry)
4. Let the retry backoff re-run setup once the server is back

import socket
from urllib.parse import urlparse

u = urlparse(url)
try:
    socket.create_connection((u.hostname, u.port or 443), timeout=5).close()
    reachable = True
except OSError:
    reachable = False

except requests.ConnectionError as err:
    raise ConfigEntryNotReady("Connection error from CalDAV server") from err

When it happens

Trigger: The configured URL cannot be connected to at all: wrong hostname, wrong port, server down, DNS resolution failure, or TLS handshake rejected before HTTP happens.

Common situations: Typo in the URL, server offline at HA startup, local DNS not resolving the CalDAV host, or the port/protocol (http vs https) mismatching the listener.

Related errors

• Timeout connecting to CalDAV server
• Credentials error from CalDAV server
• CalDAV client error
• CalDAV lookup error: {err}
• CalDAV delete error: {err}

AI-assisted analysis of home-assistant/core@58a3fdb3ea (2026-08-14). Data as JSON: /api/errors/01dd5520d6542fdb. Report an issue: GitHub.