InetAddress 代表 IP

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Net1 {
    public static void main(String[] args) {
        InetAddress inet1 = null;
        InetAddress inet2 = null;
        try {
            inet1 = InetAddress.getByName("192.168.5.76");  // the output is: /192.168.5.76
            inet2 = InetAddress.getByName("www.baidu.com"); // the output is:  www.baidu.com/104.193.88.123
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
        System.out.println(inet1);
        System.out.println(inet2);
    }
}
 

An Example

Client

 @Test
    public void testClient(){
        Socket socket = null;
        OutputStream os = null;
        try {
            InetAddress inet = InetAddress.getByName("127.0.0.1");
            socket = new Socket(inet, 22250);
            os = socket.getOutputStream();
            os.write("hello".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(os != null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

 

Server

  @Test
    public void testServer(){
        ServerSocket ss = null;
        Socket accept = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            ss = new ServerSocket(22250);
            accept = ss.accept();  // this step get  the socket of the client
            is = accept.getInputStream();

//        byte[] buf = new byte[1024];
//        int len;
//        while((len = is.read(buf)) != -1){
//            String str = new String(buf, 0, len);
//            System.out.println(str);
//        }

            baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[5];
            int len;
            while((len = is.read(buffer)) != -1){
                baos.write(buffer, 0, len);
            }
            System.out.println(baos.toString());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(is != null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(baos != null){
                try {
                    baos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(accept != null){
                try {
                    accept.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(ss != null){
                try {
                    ss.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }


    }

 

This time send a FILE

the Client

  @Test
    public void testClient2(){
        Socket socket = null;
        BufferedInputStream bis = null;
        OutputStream os = null;
        try {
            InetAddress inet = InetAddress.getByName("127.0.0.1");
            socket = new Socket(inet, 22250);
            bis = new BufferedInputStream(new FileInputStream(new File("/Users/zhuya/Pictures/Lady.jpg")));

            os = socket.getOutputStream();

            byte[] buf = new byte[1024];
            int len;
            while ((len = bis.read(buf)) != -1){
                os.write(buf,0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

the Server

  @Test
    public void testServer2(){
        ServerSocket ss = null;
        Socket socket = null;
        InputStream is = null;
        BufferedOutputStream bos = null;
        try {
            ss = new ServerSocket(22250);
            socket = ss.accept();
            is = socket.getInputStream();
            bos = new BufferedOutputStream(new FileOutputStream(new File("/Users/zhuya/Desktop/lady.jpg")));

            int len;
            byte[] buf = new byte[1024];
            while ((len = is.read(buf)) != -1){
                bos.write(buf, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bos != null) {
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(is != null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(socket != null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (ss != null) {
                try {
                    ss.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

UDP example

sender

 @Test
    public void sender(){
        DatagramSocket socket = null;
        try {
            socket = new DatagramSocket();
            // watch the packet
            String str = "This is UDP speaking";
            InetAddress inet = InetAddress.getByName("127.0.0.1");
            DatagramPacket packet = new DatagramPacket(str.getBytes(), 0, str.getBytes().length, inet, 22250);

            socket.send(packet);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {

            if (socket != null) {
                socket.close();
            }
        }
    }

receiver

    @Test
    public void receiver(){
        DatagramSocket socket = null;
        try {
            socket = new DatagramSocket(22250);

            byte[] buffer = new byte[100];
            DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
            socket.receive(packet);

            System.out.println(new String(packet.getData(), 0, packet.getLength()));
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (socket != null) {
                socket.close();
            }
        }
    }

URL

  @Test
    public void URLTest(){
        URL url = null;
        try {
            url = new URL("http://www.baidu.com/search_result.jsp?search_id=3731&search_type=search_videos");
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        System.out.println(url.getProtocol());
        System.out.println(url.getPort());
        System.out.println(url.getHost());
        System.out.println(url.getPath());
        System.out.println(url.getFile());
        System.out.println(url.getQuery());
    }