Java Tcp网络编程

示例 1：从网络上获取资源

package shiyan;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

public class URLTest {
    
    
    public static void main(String[] args) {
    
    
        try {
    
    
            //创建URL对象
            URL url = new URL("http://www.dgut.edu.cn");
            //打开url的连接
            URLConnection urlConnection = url.openConnection();
            //得到内容的长度
            int length = urlConnection.getContentLength();
            //得到输入流
            InputStream in = urlConnection.getInputStream();
            //以下从输入流读取资源保存到本地文件中
            byte[] buffer = new byte[512];
            //创建输出流对象
            FileOutputStream fileOutputStream = new FileOutputStream("test.html");
            int count = in.read(buffer);

            while(count!=-1){
    
    
                fileOutputStream.write(buffer,0,count);
                //更新读取
                count = in.read(buffer);
            }
            //关闭输入流
            in.close();
            //关闭输出流
            fileOutputStream.close();
        } catch (MalformedURLException e) {
    
    
            e.printStackTrace();
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
    }
}

示例 2：服务器和客户端通话

服务器代码:

package shiyan;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class TcpServer {
    
    
    //选择一个端口进行开放
    public static int PORT = 8080;

    public static void main(String[] args) throws IOException {
    
    
        //创建一个ServerSocket
        ServerSocket s = new ServerSocket(PORT);
        System.out.println("Started: "+s);

        //创建Socket，调用ServerSocket的accept()方法等待客户端连接
        //监听连接
        Socket socket = s.accept();

        //以下是服务器端和客户端进行数据的接受和传输
        System.out.println("Connection accepted: "+socket.getLocalPort());
        //创建字符读取缓冲区
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        //创建PrintWriter对象向客户端发送消息
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
        while(true){
    
    
            String str = in.readLine();
            if(str.equals("END")){
    
    
                break;
            }
            //打印从客户端发来的消息
            System.out.println("Echoing: "+str);
            //向客户端回传该条信息 证明服务器已接收该信息
            out.println("服务器已接收来自客户端的消息");
        }
        System.out.println("closing");
        //将socket关闭
        socket.close();
        //将Serversocket关闭
        s.close();
    }
}

客户端代码:

package shiyan;

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

public class TcpClient {
    
    
    public static void main(String[] args) throws IOException {
    
    
        //得到本地ip地址，因为我们是通过本地来创建服务器的
        InetAddress addr = InetAddress.getByName(null);
        //打印本地ip地址
        System.out.println("addr = "+addr);
        //创建socket对象,无论是服务器还是客户端，都要创建socket对象，不同的是，服务器通过Serversocket的accept()方法来创建socket对象()
        //连接服务器的8080端口
        Socket socket = new Socket(addr,8080);

        System.out.println("socket = "+socket);

        //创建BufferedReader对象来读取来自服务器的回响
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        //创建PrintWriter对象向服务器发送消息
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);

        //从客户端的控制台输入消息
        BufferedReader sysin = new BufferedReader(new InputStreamReader(System.in));

        while(true){
    
    
            //获取控制台输入的内容
            String str = sysin.readLine();
            //将控制台输入的内容发送给服务器
            out.println(str);
            if(str.equals("END")){
    
    
                break;
            }
            //获取从服务器回响的消息
            String str1 = in.readLine();
            //打印服务器回响的消息
            System.out.println(str1);
        }
        System.out.println("client closing...");
        socket.close();

    }
}

客户端运行结果

服务器端运行结果

注意：程序启动时要先启动服务器，然后启动客户端。