Netty: Process remaining inbound data in exceptionCaught - exception

Question

I need to build a very simple netty TCP server handling data sending from client. The server need to send back the result but it's not necessary for client to receive. So it may throw an exception caused by sending results after client close the connection. The channel seems stall then, but what I need server to do is continue to finish all data reading & processing.
public class TCPServerHandler extends ChannelHandlerAdapter {
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
ByteBuf in = (ByteBuf) msg;
String str = new String();
String retstr;
try {
while (in.isReadable()) {
char c = (char) in.readByte();
if (c != '\n' && c != '\r' && c != SEP_BYTE) {
str += c;
}
}
retstr = dosomething(str);
ByteBuf ok = Unpooled.copiedBuffer(retstr, CharsetUtil.UTF_8);
ctx.writeAndFlush(ok);//May trigger exceptionCaught when flushing
} catch (Throwable e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
ReferenceCountUtil.release(msg);
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
// Close the connection when an exception is raised.
System.out.println("ExceptionCaught: sending channel closed by client");
//cause.printStackTrace();
//ctx.read();//not working
//ctx.close();
}
}
So how can I ask netty to continue "channelRead" all the messages already in the buffer when exception caught?