Java网络编程

IP地址

• 本机localhost：127.0.0.1
• InetAddress
  • 通过静态方法获取实例

Socket

• InetSocketAddress

简单TCP通信

Server：

public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            //1.建立服务端口
            serverSocket = new ServerSocket(9999);
            while (true) {
                //2.等待客户端连接，获取客户端socket
                socket = serverSocket.accept();
                //3.接收用户消息
                is = socket.getInputStream();
                baos = new ByteArrayOutputStream();
                byte[] buffer = new byte[1024];
                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(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(serverSocket != null){
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

Client：

public static void main(String[] args) {
        Socket socket = null;
        OutputStream os= null;
        try {
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            //1.连接服务器
            socket = new Socket(serverIP, port);
            //2.发送消息
            os = socket.getOutputStream();
            os.write("你好".getBytes(StandardCharsets.UTF_8));
            socket.shutdownOutput();
        } 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();
                }
            }
        }
    }

简单UDP通信

Server：

public static void main(String[] args) throws Exception{
        DatagramSocket socket = new DatagramSocket(9090);
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
        socket.receive(packet);//阻塞接收
        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0, packet.getLength()));
        socket.close();
    }

Client：

	public static void main(String[] args) throws Exception{
        DatagramSocket socket = new DatagramSocket();
        String msg = "你好";
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);
        socket.send(packet);
    }

URL

通过URL获取资源：

HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.getInputStream();
...
urlConnection.disconnect();