@Override
 public void channelInactive(ChannelHandlerContext ctx) throws Exception {
   slave.onChannelInactive(ctx);
 }
 @Override
 public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
   slave.onExceptionCaught(ctx, cause);
 }
 @Override
 protected void channelRead0(ChannelHandlerContext ctx, ModbusTcpPayload msg) throws Exception {
   slave.onChannelRead(ctx, msg);
 }