private function setDeviceToken($deviceToken)
	{
		// Check if a devicetoken is given
		if (null == $deviceToken) {
			throw new \InvalidArgumentException('No device token given.');
		}

		// Check if the devicetoken is a valid hexadecimal string
		if (!ctype_xdigit($deviceToken)) {
			throw new \InvalidArgumentException('Invalid device token given, no hexadecimal: ' . $deviceToken);
		}

		// Check if the length of the devicetoken is correct
		if (64 != strlen($deviceToken)) {
			throw new \InvalidArgumentException('Invalid device token given, incorrect length: ' . $deviceToken . ' (' . strlen($deviceToken) . ')');
		}

		// Set the devicetoken
		$this->deviceToken = $deviceToken;
	}