如何在没有工作组终止的情况下正确关闭 netty 通道

Question

I have following binding to handle UDP packets

 private void doStartServer() {
        final UDPPacketHandler udpPacketHandler = new UDPPacketHandler(messageDecodeHandler);
        workerGroup = new NioEventLoopGroup(threadPoolSize);

        try {
            final Bootstrap bootstrap = new Bootstrap();
            bootstrap
                .group(workerGroup)
                .handler(new LoggingHandler(nettyLevel))
                .channel(NioDatagramChannel.class)
                .option(ChannelOption.SO_BROADCAST, true)
                .handler(udpPacketHandler);

            bootstrap
                .bind(serverIp, serverPort)
                .sync()
                .channel()
                .closeFuture()
                .await();
        } finally {
            stop();
        }
    }

and handler

@ChannelHandler.Sharable    << note this
@Slf4j
@AllArgsConstructor
public class UDPPacketHandler extends SimpleChannelInboundHandler<DatagramPacket> {

    private final MessageP54Handler messageP54Handler;

    @Override
    public void channelReadComplete(final ChannelHandlerContext ctx) {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(final ChannelHandlerContext ctx, final Throwable cause) {
        log.error("Exception in UDP handler", cause);
        ctx.close();
    }
}

At some point I get this exception java.net.SocketException: Network dropped connection on reset: no further information which is handled in exceptionCaught . This triggers ChannelHandlerContext to close. And at this point whole my server stops (executing on finnaly block from first snippet)

How to correctly handle exception so that I can handle new connections even after such exception occurs?

Answer 1

you shouldn't close the ChannelHandlerContext on an IOException when using a DatagramChannel . As DatagramChannel is "connection-less" the exception is specific to one "receive" or one "send" operation. So just log it (or whatever you want to do) and move on.