org.apache.dubbo.remoting.exchange.support.DefaultFuture#closeChannel doesn't work as expected since the channel instances to be compared do not have correct equals() implementation:

```java
 public static void closeChannel(Channel channel) {
        for (Map.Entry<Long, Channel> entry : CHANNELS.entrySet()) {
            if (channel.equals(entry.getValue())) { // in netty4, channel is NettyChannel, but entry.getValue() is NettyClient, equals will return false.
                DefaultFuture future = getFuture(entry.getKey());
                if (future != null && !future.isDone()) {
                    Response disconnectResponse = new Response(future.getId());
                    disconnectResponse.setStatus(Response.CHANNEL_INACTIVE);
                    disconnectResponse.setErrorMessage("Channel " +
                            channel +
                            " is inactive. Directly return the unFinished request : " +
                            future.getRequest());
                    DefaultFuture.received(channel, disconnectResponse);
                }
            }
        }
    }
```

This is the root cause of issue 1 in  #1968.
private static final Logger logger = LoggerFactory.getLogger(NettyClient.class);
    /**
     * netty client bootstrap
     */
    private static final NioEventLoopGroup nioEventLoopGroup = new NioEventLoopGroup(Constants.DEFAULT_IO_THREADS, new DefaultThreadFactory("NettyClientWorker", true));
    private static final String SOCKS_PROXY_HOST = "socksProxyHost";
    private static final String SOCKS_PROXY_PORT = "socksProxyPort";
    private static final String DEFAULT_SOCKS_PROXY_PORT = "1080";
    private Bootstrap bootstrap;
    /**
     * current channel. Each successful invocation of {@link NettyClient#doConnect()} will
     * replace this with new channel and close old channel.
     * <b>volatile, please copy reference to use.</b>
     */
    private volatile Channel channel;
    /**
     * The constructor of NettyClient.
     * It wil init and start netty.
     */
    public NettyClient(final URL url, final ChannelHandler handler) throws RemotingException {