一、模型说明

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采用BIO通信模型的服务端，通常由一个独立的Acceptor线程负责监听来自客户端的连接，接收到客户端请求后产生一个新的线程进行链路处理，处理完毕后通过输出流返回给客户端，线程销毁。
该模型最大的问题就是缺乏弹性伸缩能力，当访问量上升之后，服务端的线程数和客户端的访问数呈1：1的正比关系。

二、代码

1、服务端代码

public class TimeServer {

    public static void main(String[] args) throws IOException {
        int port = 8080;

        ServerSocket server = null;
        try {

            server = new ServerSocket(port);

            System.out.println("the time server is start in port : " + port);

            Socket socket = null;

            while (true){
                socket = server.accept();
                new Thread(new TimeServerHandler(socket)).start();
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (server!=null){
                server.close();
                server = null;
            }
        }
    }
}

public class TimeServerHandler implements Runnable{
    private Socket socket;

    public TimeServerHandler(Socket socket){
        this.socket = socket;
    }

    @Override
    public void run() {
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            in = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
            out = new PrintWriter(this.socket.getOutputStream(), true);
            String body = null;

            while (true) {
                body = in.readLine();

                if(body==null){
                    break;
                }

                System.out.println("the time server receive msg : " + body);

                String responseStr = "now time is : " + System.currentTimeMillis();

                out.println(responseStr);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (in!=null){
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (out!=null){
                out.close();
                out = null;
            }
            if (this.socket!=null){
                try {
                    this.socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                this.socket = null;
            }
        }
    }
}

2、客户端代码

public class TimerClient {

    public static void main(String[] args) {
        int port = 8080;
        Socket socket = null;
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            socket = new Socket("127.0.0.1", port);

            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);

            out.println("what time is now ?");

            System.out.println("the time client send msg succeed");

            String responsStr = in.readLine();

            System.out.println("the time server response --- " + responsStr);

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (out!=null){
                out.close();
                out = null;
            }
            if (in!=null){
                try {
                    in.close();
                    in = null;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                socket = null;
            }
        }
    }
}

三、运行结果

1、服务端

the time server is start in port : 8080
the time server receive msg : what time is now ?

2、客户端端

the time client send msg succeed
the time server response --- now time is : 1528517383573