IO输入流flush()

package SocketTests;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

class Server 
{
    public static void main(String[] args) throws IOException {
        new Server(new ServerSocket(3001)).run();
    }
    private ServerSocket server;
    Socket s=null;
    public Server(ServerSocket server) {
        super();
        this.server = server;
    }
    public void run()
    {
        try {
            while(true)
            {
                s=server.accept();
                InputStream is=s.getInputStream();
                BufferedReader br=new BufferedReader(new InputStreamReader(is));
                char[]buf=new char[1024];
                int i;
                while((i=br.read(buf))>0)
                System.out.println("server receive: "+new String(buf));
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally
        {
            try {
                if(server!=null)
                server.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

package SocketTests;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

public class TCPTest {
    public static void main(String[] args) throws IOException {
        new Client(new Socket(InetAddress.getLocalHost(),3001)).run();
    }
}

class Client  
{
    private Socket client;
    
    public Client(Socket client) {
        super();
        this.client = client;
    }

    public void run()
    {
        try {
            OutputStream os=client.getOutputStream();
            BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(os));
            Scanner scanner=new Scanner(System.in);
            String str;
            while(scanner.hasNextLine())
            {
                str=scanner.nextLine();
                bw.write(str);
                System.out.println("client write: "+str);
                bw.flush();//刷新流的缓冲，没有这行代码，数据没有写进，服务端调用bw.readLine()将一直堵塞
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally
        {
            try {
                if(client!=null)
                    
                client.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
    }
}