I'm trying to close my UDT server (Netty 4.0.5.Final) with shutDownGracefully() and reopen it on the same port. Unfortunately, I always get the socket exception below although it waits until the future has completed. I also added the socket option SO_REUSEADDR.

What is the proper way to do this?

Exception in thread "main" com.barchart.udt.ExceptionUDT: UDT Error : 5011 : another socket is already listening on the same UDP port : listen0:listen [id: 0x323d3939]
at com.barchart.udt.SocketUDT.listen0(Native Method)
at com.barchart.udt.SocketUDT.listen(SocketUDT.java:1136)
at com.barchart.udt.net.NetServerSocketUDT.bind(NetServerSocketUDT.java:66)
at io.netty.channel.udt.nio.NioUdtAcceptorChannel.doBind(NioUdtAcceptorChannel.java:71)
at io.netty.channel.AbstractChannel$AbstractUnsafe.bind(AbstractChannel.java:471)
at io.netty.channel.DefaultChannelPipeline$HeadHandler.bind(DefaultChannelPipeline.java:1006)
at io.netty.channel.DefaultChannelHandlerContext.invokeBind(DefaultChannelHandlerContext.java:504)
at io.netty.channel.DefaultChannelHandlerContext.bind(DefaultChannelHandlerContext.java:487)
at io.netty.channel.ChannelDuplexHandler.bind(ChannelDuplexHandler.java:38)
at io.netty.handler.logging.LoggingHandler.bind(LoggingHandler.java:254)
at io.netty.channel.DefaultChannelHandlerContext.invokeBind(DefaultChannelHandlerContext.java:504)
at io.netty.channel.DefaultChannelHandlerContext.bind(DefaultChannelHandlerContext.java:487)
at io.netty.channel.DefaultChannelPipeline.bind(DefaultChannelPipeline.java:848)
at io.netty.channel.AbstractChannel.bind(AbstractChannel.java:193)
at io.netty.bootstrap.AbstractBootstrap$2.run(AbstractBootstrap.java:321)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:354)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:366)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101)
at java.lang.Thread.run(Thread.java:724)

A small test program demonstration the problem:

public class MsgEchoServer {

    public static class MsgEchoServerHandler extends ChannelInboundHandlerAdapter {
    }

    public void run() throws Exception {
        final ThreadFactory acceptFactory = new UtilThreadFactory("accept");
        final ThreadFactory connectFactory = new UtilThreadFactory("connect");
        final NioEventLoopGroup acceptGroup = new NioEventLoopGroup(1,
                acceptFactory, NioUdtProvider.MESSAGE_PROVIDER);
        final NioEventLoopGroup connectGroup = new NioEventLoopGroup(1,
                connectFactory, NioUdtProvider.MESSAGE_PROVIDER);
        try {
            final ServerBootstrap boot = new ServerBootstrap();
            boot.group(acceptGroup, connectGroup)
                .channelFactory(NioUdtProvider.MESSAGE_ACCEPTOR)
                .option(ChannelOption.SO_BACKLOG, 10)
                .option(ChannelOption.SO_REUSEADDR, true)
                .handler(new LoggingHandler(LogLevel.INFO))
                .childHandler(new ChannelInitializer<UdtChannel>() {
                    @Override
                    public void initChannel(final UdtChannel ch) throws Exception {
                        ch.pipeline().addLast(new MsgEchoServerHandler());
                    }
                });
            final ChannelFuture future = boot.bind(1234).sync();
        } finally {
            acceptGroup.shutdownGracefully().syncUninterruptibly();
            connectGroup.shutdownGracefully().syncUninterruptibly();
        }
        new MsgEchoServer().run();
    }

    public static void main(final String[] args) throws Exception {
        new MsgEchoServer().run();
    }

}