Get underlying error code on remote channel. Possible remote channel error code are:
NOT_ATTACHED: If the target remote device is not attached to the basestation (the device is offline).
TIMEOUT: If a timeout occured when connecting to the basestation.
FORBIDDEN: If the basestation request is rejected.
TOKEN_REJECTED: If the basestation rejected based on an invalid SCT or JWT.
DNS: If the server URL failed to resolve.
UNKNOWN_SERVER_KEY: If the provided server key was not known by the basestation.
UNKNOWN_PRODUCT_ID: If the provided product ID was not known by the basestation.
UNKNOWN_DEVICE_ID: If the provided device ID was not known by the basestation.
NONE: If remote relay was not enabled.
OPERATION_IN_PROGRESS: if the opening of the channel is still in progress.
INVALID_STATE: if required options are missing for the remote connection
CONNECTION_REFUSED: if the client could not connect to the basestation.
the remote channel error code