网络编程

1.网络通信要素

2.IP

3.端口号

4.通信协议

TCP : 打电话

UDP : 发短信 , 发电报

4.1 TCP

public class TCPtest {
    //客户端发送消息给服务端 , 服务端将信息显示在控制台
    
    //客户端
    @Test
    public void client() {
        Socket socket = null;
        OutputStream outputStream = null;
        try {
            //获取服务端的socket
            InetAddress address = InetAddress.getByName("127.0.0.1");
            socket = new Socket(address, 8899);
            //通过socket 获取输出流 , 发送信息
            outputStream = socket.getOutputStream();
            outputStream.write("你好,我是客户端mm".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    //服务端
    @Test
    public void server() {
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream inputStream = null;
        ByteArrayOutputStream byteArrayOutputStream = null;
        try {
            //创建serverSocket
            serverSocket = new ServerSocket(8899);
            //接收客户端的socket
            socket = serverSocket.accept();
            //创建接受流
            inputStream = socket.getInputStream();
            //打印信息
            byteArrayOutputStream = new ByteArrayOutputStream();
            byte[] buffer = new byte[5];
            int len;
            while ((len = inputStream.read(buffer)) != -1) {
                byteArrayOutputStream.write(buffer, 0, len);
            }
            System.out.println(byteArrayOutputStream.toString());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                byteArrayOutputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                inputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                serverSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

4.2 UDP

public class UDPtest {
    //测试用UDP协议 发送和 接收数据

    //发送端
    @Test
    public void sender()throws IOException {
        DatagramSocket datagramSocket = new DatagramSocket();
        String str = "我是UDP方式发送的数据!";
        InetAddress address = InetAddress.getByName("localhost");
        DatagramPacket packet = new DatagramPacket(str.getBytes(), 0, str.getBytes().length, address, 9090);
        //发送
        datagramSocket.send(packet);
        //关闭socket
        datagramSocket.close();
    }

    //接收端
    @Test
    public void receiver()throws IOException{
        DatagramSocket socket = new DatagramSocket(9090);
        byte[] buffer = new byte[100];
        DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);
        //接收
        socket.receive(packet);
        System.out.println(new String(packet.getData(),0,packet.getLength()));
        //关闭
        socket.close();
    }
}

5.URL

//从Tomcat中下载图片

    @Test
    public void test()throws IOException {
        URL url = new URL("http://localhost:8080/examples/picture.jpg");
        //获取链接
        HttpURLConnection urlConnection =(HttpURLConnection) url.openConnection();
        urlConnection.connect();
        //获取输入 , 输出流
        InputStream inputStream = urlConnection.getInputStream();
        FileOutputStream fileOutputStream = new FileOutputStream("picture1.jpg");
        //传输数据
        byte[] buffer = new byte[5];
        int len;
        while ((len=inputStream.read(buffer))!=-1){
            fileOutputStream.write(buffer,0,len);
        }
        System.out.println("下载完成!");
        //关闭资源
        fileOutputStream.close();
        inputStream.close();
        urlConnection.disconnect();
    }