    function updateChannel(string calldata from, string calldata to, address _address) external onlyMaster onlyWhenNotStopped
    {
        require(bytes(from).length > 0);
        require(bytes(to).length > 0);
        require(addressMap[to] == address(0));
        addressMap[to] = _address;
        addressMap[from] = address(0);
        emit UpdateAddress(from, to);
    }