网络编程（含 UrlConnection 发送 HTTP 请求下载文件）

朱雀 2023-10-03 10:56 105阅读 0赞

#### 文章目录 ####

*   *   *   *  一、网络模型
             *  二、获取 IP
             *  三、TCP 协议
             *   *  1、建立连接
                 *  2、上传文件
             *  四、UDP 协议
             *  五、下载网络资源

*  网络编程（含 UrlConnection 发送 HTTP 请求下载文件）：[https://blog.csdn.net/qq\_41538097/article/details/118722718][https_blog.csdn.net_qq_41538097_article_details_118722718]
 *  Apache HttpComponents 简单使用：[https://blog.csdn.net/qq\_41538097/article/details/123719298][https_blog.csdn.net_qq_41538097_article_details_123719298]
 *  RestTemplate简单使用：[https://blog.csdn.net/qq\_41538097/article/details/123560238][https_blog.csdn.net_qq_41538097_article_details_123560238]
 *  okhttp3简单使用：[https://blog.csdn.net/qq\_41538097/article/details/123677614][https_blog.csdn.net_qq_41538097_article_details_123677614]
 *  HttpURLConnection 简单使用：[https://blog.csdn.net/qq\_41538097/article/details/123697432][https_blog.csdn.net_qq_41538097_article_details_123697432]

##### 一、网络模型 #####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTM4MDk3_size_16_color_FFFFFF_t_70]

##### 二、获取 IP #####

通过 InetAddress 类获取 IPv4 地址

InetAddress localhost = InetAddress.getByName("localhost"); 
            System.out.println(localhost); // localhost/127.0.0.1
    
            System.out.println(InetAddress.getLocalHost()); // LingyueYe/192.168.3.185
            InetAddress localHost = InetAddress.getLocalHost();
            System.out.println(localHost.getHostAddress()); // 192.168.3.185
            System.out.println(localHost.getHostName()); // LingyueYe

如果你有多个网卡可以获取全部的 IPv4 地址

private static List<String> getIpAddress() throws SocketException {
        
            List<String> list = new LinkedList<>();
            Enumeration<NetworkInterface> enumeration = NetworkInterface.getNetworkInterfaces();
            while (enumeration.hasMoreElements()) {
        
                NetworkInterface network = enumeration.nextElement();
                Enumeration<InetAddress> addresses = network.getInetAddresses();
                while (addresses.hasMoreElements()) {
        
                    InetAddress address = addresses.nextElement();
                    if (address instanceof Inet4Address) {
        
                        list.add(address.getHostAddress());
                    }
                }
            }
            return list;
        }

# 我电脑装了虚拟机有四个 IP 地址
    list：[127.0.0.1, 192.168.159.1, 192.168.1.1, 192.168.3.240]

##### 三、TCP 协议 #####

###### 1、建立连接 ######

*  建立服务端监听客户端连接，一定要手动关闭连接，否则 java 自动关闭连接会报错

public static void main(String[] args) throws IOException {
        
            ServerSocket serverSocket = new ServerSocket(9997);
    
            Socket accept = serverSocket.accept();
            InputStream inputStream = accept.getInputStream();
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            byte[] bytes = new byte[1024];
            int len;
            while((len=inputStream.read(bytes))!=-1){
        
                byteArrayOutputStream.write(bytes,0,len);
            }
            System.out.println(new String(bytes));
            byteArrayOutputStream.close();
            inputStream.close();
            accept.close();
            serverSocket.close();
        }

*  建立客户端连接服务端，一定要手动关闭连接，否则 java 自动关闭连接会报错

public static void main(String[] args) throws IOException {
        
            InetAddress localhost = InetAddress.getByName("1.117.165.107");
            int port = 9997;
            System.out.println(localhost.getHostAddress());
            Socket socket = new Socket(localhost.getHostAddress(), port);
            OutputStream outputStream = socket.getOutputStream();
            outputStream.write("学习网络编程".getBytes());
            outputStream.close();
            socket.close();
        }

连接成功  
![在这里插入图片描述][2021071417002662.png]

###### 2、上传文件 ######

*  客户端

public static void main(String[] args) throws IOException {
        
            System.out.println("请输入上传的的文件名路径");
            Scanner scanner = new Scanner(System.in);
            String next = scanner.next();
            Socket socket = new Socket("1.117.165.107", 9997);//
            OutputStream outputStream = socket.getOutputStream();
            InputStream inputStream = new FileInputStream(new File("src/main/java/com/ye/"+next));
    
            byte[] bytes = new byte[20];
            int len;
            while((len=inputStream.read(bytes))!=-1){
        
                outputStream.write(bytes,0,len); off 偏移量，偏移量0 代表紧跟追加，将 bytes.length 的字节写入文件（追加的形式）
            }
                    // 通知服务器，我已经写入完毕
            socket.shutdownInput();
            // 判断是否写入完毕
            socket.isInputShutdown();
            socket.shutdownInput();
            socket.isOutputShutdown();
            socket.isConnected();
            socket.isClosed();
            inputStream.close();
            outputStream.close();
            socket.close();
        }

*  服务端

public static void main(String[] args) throws IOException {
        
            ServerSocket serverSocket = new ServerSocket(9997);
            Socket accept = serverSocket.accept();
            InputStream inputStream = accept.getInputStream();
            String fileName = UUID.randomUUID().toString().replace("-", "")+".txt";
            OutputStream outputStream = new FileOutputStream(new File(fileName));
            byte[] bytes = new byte[1024];
            int len;
    
            while ((len = inputStream.read(bytes)) != -1) {
        
                outputStream.write(bytes, 0, len);
            }
            outputStream.close();
            inputStream.close();
            accept.close();
            serverSocket.close();
        }

*  运行结果  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTM4MDk3_size_16_color_FFFFFF_t_70 1]

##### 四、UDP 协议 #####

无状态协议

*  客户端

public static void main(String[] args) throws IOException {
        
    
            // 使用 connect() 连接远程地址，数据包只能发送到或从该地址接收。
            // 建立一个 socket，该客户端端口号 9998
            DatagramSocket datagramSocket = new DatagramSocket(9998);
    
            String str = "你好呀！UDP";
    		// 连接 9997 客户端，将包裹发送到指定 9997 端口
            datagramSocket.connect(InetAddress.getByName("127.0.0.1"), 9997);
            // 需要发送的数据
            DatagramPacket datagramPacket = new DatagramPacket(str.getBytes(), 0, str.getBytes().length);
    
            datagramSocket.send(datagramPacket);
            datagramSocket.close();
    
    
            // DatagramPacket 指定数据包发的地址
            DatagramSocket datagramSocket2 = new DatagramSocket();
    
            String str2 = "你好呀！UDP2";
            // 需要发送的数据
            DatagramPacket datagramPacket2 = new DatagramPacket(str2.getBytes(), 0, str2.getBytes().length, InetAddress.getByName("127.0.0.1"), 9997);
            datagramSocket2.send(datagramPacket2);
            datagramSocket2.close();
        }

*  服务端

public static void main(String[] args) throws IOException {
        
            DatagramSocket datagramSocket = new DatagramSocket(9997);
    		// 准备接收包裹
            byte[] bytes = new byte[1024];
            DatagramPacket datagramPacket = new DatagramPacket(bytes,0,bytes.length);
    
            while (true) {
        
                datagramSocket.receive(datagramPacket); // 阻塞接收
    
                System.out.println(datagramPacket.getAddress());
    
                System.out.println(new String(datagramPacket.getData(),0,datagramPacket.getLength()));
            }
        }

*  测试连接  
    ![在这里插入图片描述][20210715004604579.png]

##### 五、下载网络资源 #####

使用 URLConnection 下载 网易云歌曲  
![在这里插入图片描述][20210715112335321.png]

public static void main(String[] args) throws IOException {
        
            URL url = new URL("https://m701.music.126.net/20210715112506/36079aa66fa5d52682401a9ad2a02e4f/jdyyaac/obj/w5rDlsOJwrLDjj7CmsOj/9836255744/326a/aad9/2c3a/a1257b6740eed2f70dc115a5ed3be1b4.m4a");
            URLConnection urlConnection = url.openConnection();
            // 如果报 Server returned HTTP response code: 403 for URL 可添加如下
            urlConnection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.51 Safari/537.36");
    
            InputStream inputStream = urlConnection.getInputStream();
            FileOutputStream fileOutputStream = new FileOutputStream(new File("123456.m4a"));
            byte[] bytes = new byte[1024];
            int len;
            while((len=inputStream.read(bytes))!=-1){
        
                fileOutputStream.write(bytes,0,len);
            }
            fileOutputStream.close();
            inputStream.close();
        }

[https_blog.csdn.net_qq_41538097_article_details_118722718]: https://blog.csdn.net/qq_41538097/article/details/118722718
[https_blog.csdn.net_qq_41538097_article_details_123719298]: https://blog.csdn.net/qq_41538097/article/details/123719298
[https_blog.csdn.net_qq_41538097_article_details_123560238]: https://blog.csdn.net/qq_41538097/article/details/123560238
[https_blog.csdn.net_qq_41538097_article_details_123677614]: https://blog.csdn.net/qq_41538097/article/details/123677614
[https_blog.csdn.net_qq_41538097_article_details_123697432]: https://blog.csdn.net/qq_41538097/article/details/123697432
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTM4MDk3_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20210714105343681.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTM4MDk3,size_16,color_FFFFFF,t_70
[2021071417002662.png]: https://img-blog.csdnimg.cn/2021071417002662.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTM4MDk3_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20210714224102227.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTM4MDk3,size_16,color_FFFFFF,t_70
[20210715004604579.png]: https://img-blog.csdnimg.cn/20210715004604579.png
[20210715112335321.png]: https://img-blog.csdnimg.cn/20210715112335321.png