Netty中的java.net.SocketException

Question

When I bind "127.0.0.1", it works without exception, but when I bind "172.16.3.138", after it runs for 15 seconds, an exception is thrown:

java.net.SocketException: Can't assign requested address:/172.16.3.138:8888

I'm using Netty-4.033 on Mac.

My Server Code：

EventLoopGroup masterGroup = null;
    EventLoopGroup workGroup = null;
    try {
        masterGroup = new NioEventLoopGroup();
        workGroup = new NioEventLoopGroup();
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(masterGroup, workGroup)
                .channel(NioServerSocketChannel.class)
                .childHandler(childHandler)
                .option(ChannelOption.SO_BACKLOG, 100)
                .childOption(ChannelOption.SO_KEEPALIVE, true);

        ChannelFuture channelFuture = serverBootstrap.bind(new InetSocketAddress("0.0.0.0",port)).sync();
        channelFuture.channel().closeFuture().sync();
    } catch (Exception e) {
        BaseLog.logger.error("netty server start failed",e);
    } finally {
        if (workGroup != null)
            workGroup.shutdownGracefully();
        if (masterGroup != null)
            masterGroup.shutdownGracefully();
    }

My client Code:

public void run() {
    EventLoopGroup group = null;
    int initTimes = 0;
    while (true) {
        try {
            if (initTimes > 50) {
                BaseLog.logger.error("try 50 times to create NioEvent,failed");
                break;
            }
            group = new NioEventLoopGroup();
            break;
        } catch (Exception e) {
            initTimes++;
            sleep(300);
            continue;
        }
    }

    try {
        Bootstrap bootstrap = new Bootstrap().group(group)
                .channel(NioSocketChannel.class)
                .handler(handler)
                .option(ChannelOption.SO_KEEPALIVE, true);

        int tryTimes = 1;
        channel = null;
        connect(bootstrap,tryTimes);
    } catch (Exception e) {
        e.printStackTrace();
        BaseLog.logger.error("try 5 times,netty client connect failed",e);
    } finally {
        if (group != null)
            group.shutdownGracefully();
    }
}
protected void connect(final Bootstrap bootstrap, final int tryTimes) throws InterruptedException, NettyConnectionException {
    if (tryTimes > 5)
        throw new NettyConnectionException("try 5 times failed");
    ChannelFuture channelFuture = null;
    if (!StringUtil.isEmpty(host) && !host.equals("127.0.0.1") && !host.equals("localhost")) {
        channelFuture = bootstrap.connect(new InetSocketAddress(host, port)).sync();
    }
    else
        channelFuture = bootstrap.connect(host, port).sync();
    if (channelFuture == null) return;
    channelFuture.addListener(new ChannelFutureListener() {
        @Override
        public void operationComplete(ChannelFuture future) throws Exception {
            if (future.isSuccess()) {
                channel = future.channel();
                sendDatas(objs);
            } else {
                connect(bootstrap, tryTimes+1);
            }
        }
    });
}

Answer 1

Are you sure the address you provide (172.16.3.138) is the address of the computer the program is running on?

Binding to an IP other than loopback and localhost is designed to bind to another network adapter (on the same computer).

Answer 2

When you are calling to 127.0.0.1:8888 you are connecting in a direct way with you own machine, and the port 8888 in that case is open. But when you call to 172.16.3.138:8888 you are connecting with you own machine too, but you need pass through a router or another server proxy which could have the port 8888 closed. Please verify this and try again. (maybe you need to open the port 8888 in you router).