传统的java BIO

网络编程基本都是使用的Client/server模型，也就是两个进程之间相互通信。服务端提供IP和端口，客户端通过连接操作向服务端监听的地址发起连接请求，通过三次握手建立连接，连接成功就可以用Socket通信（ServerSocke负责绑定IP，启动监听端口，socket发起连接，连接成功后，通过IO流进行同步阻塞通信）。
今天以一个TimeServer回顾
直接上代码

package BIO;

/**
 * Created by zhangguanlong on 2017/12/28.
 */
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class TimeServer {
    public static void main(String[] args) throws IOException {
        int port = 8380;
        if (args != null&& args.length>0) {
            port=Integer.valueOf(args[0]);
        }
        ServerSocket server = null;
        try {
            server= new ServerSocket(port);
            System.out.println("The time server is start on port:"+port);
            Socket socket =null;
            while (true) {
                socket=server.accept();
                new Thread(new TimeServerHandler(socket)).start();
            }
        } catch (Exception e) {
            // TODO: handle exception
        }finally {
            if (server != null) {
                System.out.println("The time server close");
                server.close();
                server = null;
            }
        }

    }

}

通过死循环监听客户端的连接，如果没有客户端接入。就会阻塞在ServerSocket的accept上
不信请看堆栈信息

"main" #1 prio=5 os_prio=0 tid=0x0000000002ae2800 nid=0x2624 runnable [0x0000000002adf000]
   java.lang.Thread.State: RUNNABLE
    at java.net.DualStackPlainSocketImpl.accept0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131)
    at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:404)
    at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199)
    - locked <0x00000000d5cb7918> (a java.net.SocksSocketImpl)
    at java.net.ServerSocket.implAccept(ServerSocket.java:545)
    at java.net.ServerSocket.accept(ServerSocket.java:513)
    at BIO.TimeServer.main(TimeServer.java:22)

   Locked ownable synchronizers:
    - None

有接入的时候构造TimeServerHandler对象，这是一个Runnerable

package BIO;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Date;
import java.net.Socket;

/**
 * Created by zhangguanlong on 2017/12/28.
 */
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 currentTime = null;
            String body = null;
            while (true) {
                body=in.readLine();
                if (body==null)
                    break;
                System.out.println("the time server recieved order:"+body);
                currentTime = "Query TIME ORDER".equalsIgnoreCase(body)?new Date(System.currentTimeMillis()).toString():"BAD ORDER";
                out.println(currentTime);

            }

        } catch (Exception e) {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
            if (out !=null) {
                out.close();
                out=null;
            }
            if (this.Socket==null) {
                try {
                    this.Socket.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                this.Socket=null;
            }
        }

    }

}

下面是客户端

package BIO;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * Created by zhangguanlong on 2017/12/28.
 */
public class TimeClient {
    public static void main(String[] args) {
        int port = 8380;
        if (args == null&&args.length>0) {
            port = Integer.valueOf(args[0]);
        }
        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(new OutputStreamWriter(socket.getOutputStream()),true);
            out.println("Query TIME ORDER");
            System.out.println("send order 2 server succeed.");
            String res = in.readLine();
            System.out.println("Now is"+res);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
            if (out !=null) {
                out.close();
                out=null;
            }
            if (socket==null) {
                try {
                    socket.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                socket=null;
            }
        }


    }
}

运行结果