Java中使用Socket网络编程

  

引言：

主要就是TCP/UDP网络通信的使用

一、TCP 网络编程

例子1：客户端发送信息给服务端，服务端将数据显示在控制台上

public class TCPTest1 {
    //客户端
    @Test
    public void client() {
        Socket socket = null;
        OutputStream os = null;
        try {
            //1. 创建Socket对象，指明服务器端的ip和端口号
            InetAddress inet = InetAddress.getByName("127.0.0.1");
            socket = new Socket(inet, 8899);
            //2. 获取一个输出流，用于输出数据
            os = socket.getOutputStream();
            //3. 写出数据
            os.write("你好，我是客户端。HaHaHa".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //4. 关闭资源
            if (os != null) {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //服务端
    @Test
    public void server() {
        ServerSocket ss = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            //1. 创建服务器端的ServerSocket，指明自己的端口号
            ss = new ServerSocket(8899);
            //2. 调用accept()表示接收来自于客户端的socket
            socket = ss.accept();
            //3. 获取输入流
            is = socket.getInputStream();

            //不建议这样写，可能会有乱码
            /*byte[] buffer = new byte[1024];
            int len;
            while((len = is.read(buffer)) != -1){
                String str = new String(buffer,0,len);
                System.out.print(str);
            }*/

            //4. 读取输入流中的数据，先写入到ByteArrayOutputStream中。然后通过toString()获取写入数据
            baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[20];
            int len;
            while ((len = is.read(buffer)) != -1) {
                baos.write(buffer, 0, len);
            }
            System.out.println(baos.toString());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //5. 关闭资源
            if (baos != null) {
                try {
                    baos.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();
                }
            }
        }
    }
}

例子2：客户端发送文件给服务端，服务端将文件保存在本地。

public class TCPTest2 {
    /*
    注意：这里涉及到的异常，应该使用try-catch-finally处理
     */
    // 客户端
    @Test
    public void client() throws IOException {
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),9090);
        OutputStream os = socket.getOutputStream();
        FileInputStream fis = new FileInputStream(new File("beauty.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while((len = fis.read(buffer)) != -1){
            os.write(buffer,0,len);
        }
        fis.close();
        os.close();
        socket.close();
    }

    /*
    注意：同样，这里涉及到的异常，应该使用try-catch-finally处理
     */
    // 服务端
    @Test
    public void server() throws IOException {
        ServerSocket ss = new ServerSocket(9090);
        Socket socket = ss.accept();
        InputStream is = socket.getInputStream();
        FileOutputStream fos = new FileOutputStream(new File("beauty1.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while((len = is.read(buffer)) != -1){
            fos.write(buffer,0,len);
        }

        fos.close();
        is.close();
        socket.close();
        ss.close();
    }
}

例子3：从客户端发送文件给服务端，服务端保存到本地。并返回“发送成功”给客户端。然后闭相应的连接。

public class TCPTest3 {
    /*
    注意：这里涉及到的异常，应该使用try-catch-finally处理
     */
    // 客户端
    @Test
    public void client() throws IOException {
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),9090);
        OutputStream os = socket.getOutputStream();
        FileInputStream fis = new FileInputStream(new File("beauty.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while((len = fis.read(buffer)) != -1){
            os.write(buffer,0,len);
        }

        //关闭数据的输出
        socket.shutdownOutput();

        //接收来自于服务器端的数据，并显示到控制台上
        InputStream is = socket.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] bufferr = new byte[20];
        int len1;
        while((len1 = is.read(buffer)) != -1){
            baos.write(buffer,0, len1);
        }
        System.out.println(baos.toString());

        fis.close();
        os.close();
        socket.close();
        baos.close();
    }

    /*
    注意：同样，这里涉及到的异常，应该使用try-catch-finally处理
     */
    // 服务端
    @Test
    public void server() throws IOException {
        ServerSocket ss = new ServerSocket(9090);
        Socket socket = ss.accept();
        InputStream is = socket.getInputStream();
        FileOutputStream fos = new FileOutputStream(new File("beauty1.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while((len = is.read(buffer)) != -1){
            fos.write(buffer,0,len);
        }
        System.out.println("文件传输完成");

        //服务端给予客户端反馈
        OutputStream os = socket.getOutputStream();
        os.write("你好，文件我收到了。Very nice".getBytes());

        fos.close();
        is.close();
        socket.close();
        ss.close();
        os.close();
    }
}

二、UDP 网络编程

public class UDPTest {

    //发送端
    @Test
    public void sender() throws IOException {
        DatagramSocket socket = new DatagramSocket();
        String str = "我是UDP方式发送的导弹";
        byte[] data = str.getBytes();
        InetAddress inet = InetAddress.getLocalHost();
        DatagramPacket packet = new DatagramPacket(data, 0, data.length, inet, 9090);

        socket.send(packet);
        socket.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);

        socket.receive(packet);
        String str = new String(packet.getData(), 0, packet.getLength());
        System.out.println(str);

        socket.close();
    }
}

三、URL资源访问

下载百度图像到本地

public class URLTest {
    public static void main(String[] args) {
        HttpURLConnection urlConnection = null;
        InputStream is = null;
        FileOutputStream fos = null;
        try {
            URL url = new URL("https://ss1.bdstatic.com/70cFvXSh_Q1YnxGkpoWK1HF6hhy/it/u=3363295869,2467511306&fm=26&gp=0.jpg");
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.connect();
            is = urlConnection.getInputStream();
            fos = new FileOutputStream("test.png");
            byte[] buffer = new byte[1024];
            int len;
            while ((len = is.read(buffer)) != -1) {
                fos.write(buffer, 0, len);
            }
            System.out.println("下载完成");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //关闭资源
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
    }
}