http can only accept limit connection at the same time

HttpHelloWorldServerHandler.java

/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.example.http.threads;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaderUtil;
import io.netty.handler.codec.http.HttpHeaderValues;
import io.netty.handler.codec.http.HttpRequest;

import static io.netty.handler.codec.http.HttpHeaderNames.*;
import static io.netty.handler.codec.http.HttpResponseStatus.*;
import static io.netty.handler.codec.http.HttpVersion.*;


public class HttpHelloWorldServerHandler extends ChannelHandlerAdapter {
    private static final byte[] CONTENT = { 'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd' };

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }
    ChannelHandlerContext ctx1;
    @Override
    public void channelRead( ChannelHandlerContext ctx, Object msg) {

        ctx1 = ctx;
        Thread t = new Thread(new Runnable(){
            public void run(){
                try {
                    Thread.sleep(60000);
                    FullHttpResponse response = new DefaultFullHttpResponse(HTTP_1_1, OK, Unpooled.wrappedBuffer(CONTENT));
                    response.headers().set(CONTENT_TYPE, "text/plain");
                    response.headers().setInt(CONTENT_LENGTH, response.content().readableBytes());
                    ctx1.writeAndFlush(response);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        t.start();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }
}