Java基础——网络通信

TCP通信

简单的通信

客户端

public class TCPClientDemo {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;

        try {
            //服务器的ip
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            //创建Socket连接
            socket = new Socket(serverIP, port);
            //发送消息流
            os = socket.getOutputStream();
            os.write("你好".getBytes());

        } catch (Exception 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();
                }
            }
        }
    }
}

服务端

public class TCPServerDemo {
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream bos = null;

        try {
            //创建服务Socket
            serverSocket =new ServerSocket(9999);
            while(true){
                //等待用户连接
                socket = serverSocket.accept();
                //读取客户端消息
                is = socket.getInputStream();
				//利用管道流接收，避免buffer溢出
                bos = new ByteArrayOutputStream();
                byte[] buffer = new byte[2048];
                int len;
                while((len = is.read(buffer)) != -1){
                    bos.write(buffer, 0, len);
                }

                System.out.println(bos.toString());
            }

        } 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 (serverSocket != null){
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

文件上传

客户端

public class TCPFileClientDemo {
    public static void main(String[] args) throws IOException {
        //创建Socket连接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9000);
        //创建输出流
        OutputStream os = socket.getOutputStream();

        //读文件
        FileInputStream fis = new FileInputStream(new File("head.jpg"));

        //写出文件
        byte[] buffer = new byte[2048];
        int len;
        while((len = fis.read(buffer)) != -1){
            os.write(buffer, 0 ,len);
        }

        socket.shutdownOutput();//关闭输出流

        InputStream is = socket.getInputStream();
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buffer2 = new byte[2048];
        int len2;
        while ((len2 = is.read(buffer2)) != -1){
            bos.write(buffer2, 0, len2);
        }

        System.out.println(bos.toString());

         //关闭资源
        fis.close();
        os.close();
        socket.close();

    }
}

接收端

public class TCPFileServerDemo {
    public static void main(String[] args) throws IOException {
        //创建服务
        ServerSocket ss = new ServerSocket(9000);
        //监听客户端连接
        Socket socket = ss.accept();
        //获取输入流
        InputStream is = socket.getInputStream();

        //输出文件
        FileOutputStream fos = new FileOutputStream(new File("head_2.jpg"));
        byte[] buffer = new byte[2048];
        int len;
        while((len = is.read(buffer)) != -1){
            fos.write(buffer, 0, len);
        }

        OutputStream os =  socket.getOutputStream();
        os.write("接收完成！".getBytes());

        //关闭资源
        fos.close();
        is.close();
        socket.close();
        ss.close();
    }
}

UDP通信

简单的字符通信

发送端

public class UDPDemo01 {
    public static void main(String[] args) throws Exception {
        //建立一个数据报Socket连接
        DatagramSocket ds = new DatagramSocket();

        String msg = "hello udp";

        //建立一个数据包
        DatagramPacket dp = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length,
                InetAddress.getByName("127.0.0.1"), 9000);

        //发送数据报
        ds.send(dp);

        //关闭流
        ds.close();
    }
}

接收端

public class UDPDemo02 {
    public static void main(String[] args) throws Exception {
        //建立一个数据报连接并开放端口
        DatagramSocket ds = new DatagramSocket(9000);

        //接收数据报
        byte[] buffer = new byte[2048];
        DatagramPacket dp = new DatagramPacket(buffer, 0, buffer.length);

        ds.receive(dp);

        System.out.println(new String(dp.getData(), 0, dp.getLength()));

        //关闭流
        ds.close();
    }
}

URL下载网络资源

public class URLDemo {
    public static void main(String[] args) throws Exception {
        //url下载地址
        URL url = new URL("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1584747495037&di=722414a50eac5e185f9e1235d6aa6dfc&imgtype=0&src=http%3A%2F%2Fimg.25pp.com%2Fuploadfile%2Fyouxi%2Fimages%2F2013%2F0201%2F20130201100918698.jpg");

        //连接到这个资源
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream is = urlConnection.getInputStream();

        FileOutputStream fos = new FileOutputStream("fisher.jpg");
        byte[] buffer = new byte[1024];
        int len;

        while((len = is.read(buffer)) != -1){
            fos.write(buffer, 0, len);
        }

        fos.close();
        is.close();
        urlConnection.disconnect();
    }
}