Java网络编程

Java网络编程笔记

1 IP地址

使用java的类InetAddress

Copypublic class TestInetAddress {
    public static void main(String[] args) {
        try {
            //本机地址
            InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
            System.out.println(inetAddress1);
            InetAddress inetAddress2 = InetAddress.getByName("localhost");
            System.out.println(inetAddress2);
            InetAddress inetAddress3 = InetAddress.getLocalHost();
            System.out.println(inetAddress3);
            //网站地址
            InetAddress inetAddress4 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress4);
            //常用方法
            System.out.println(inetAddress4.getAddress());
            System.out.println(inetAddress4.getCanonicalHostName());
            System.out.println(inetAddress4.getHostAddress());
            System.out.println(inetAddress4.getHostName());
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

2 端口

端口表示计算机上的程序的一个进程

• 0 ~ 65535
• 不同进程不同端口号，不能冲突
• TCP和UDP有各自的端口号，不冲突

public class TestInetSocketAddress {
    public static void main(String[] args) {
        InetSocketAddress socketAddress1 = new InetSocketAddress("127.0.0.1", 8080);
        InetSocketAddress socketAddress2 = new InetSocketAddress("localhost", 8080);
        System.out.println(socketAddress1);
        System.out.println(socketAddress2);
        
        System.out.println(socketAddress1.getAddress());
        System.out.println(socketAddress1.getHostName());
        System.out.println(socketAddress1.getPort());
    }
}

3 通信协议

• TCP
  • 连接，稳定
  • 三次握手，四次挥手
  • 客户端与服务端之间
  • 传输完成，释放连接，效率低
• UDP
  • 不连接，不稳定
  • 客户端与服务端没有明确的界限
  • 不管有没有准备好都可以发送

4 TCP

客户端

1. 连接服务器 Socket
2. 发送消息

服务端

1. 建立服务的端口 ServerSocket
2. 等待用户的连接 accept
3. 接收消息

Copy//客户端
public class TcpClientDemo {
    public static void main(String[] args) {
        Socket socket = null;
        OutputStream os = null;
        try {
            //获取服务器的地址，端口号
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port = 8888;
            //创建socket连接
            socket = new Socket(serverIP, port);
            //发送消息
            os = socket.getOutputStream();
            os.write("test connection".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();
                }
            }
        }
    }
}
Copy//服务端
public class TcpServerDemo {
    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        Socket socket = null;
        InputStream is = null;
        ByteArrayOutputStream baos = null;
        try {
            //设定服务器的地址
            serverSocket = new ServerSocket(8888);
            //等待客户端连接
            socket = serverSocket.accept();
            //读取客户端的消息
            is = socket.getInputStream();
            //管道流
            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 {
            //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 (serverSocket != null) {
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

5 TCP实现文件上传

Copypublic class TcpClientDemo {
    public static void main(String[] args) throws Exception {
        //创建Socket连接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9999);
        //创建输出流
        OutputStream os = socket.getOutputStream();
        //读取文件
        FileInputStream fis = new FileInputStream(new File("test.jpg"));
        //写出文件
        byte[] buffer = new byte[1024];
        int len;
        while ((len = fis.read(buffer)) != -1) {
            os.write(buffer, 0, len);
        }
        
        //通知服务器传输结束
        socket.shutdownOutput();
        
        //确定服务端接收完毕才能断开连接
        InputStream is = socket.getInputStream();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer2 = new byte[1024];
        int len2;
        while ((len2 = is.read(buffer2)) != -1) {
            baos.write(buffer2, 0, len2);
        }
        System.out.println(baos.toString());
        
        //关闭资源
        baos.close();
        is.close()
        fis.close();
        os.close();
        socket.close();
    }
}
Copypublic class TcpServerDemo {
    public static void main(String[] args) throws Exception {
        //创建端口
        ServerSocket serverSocket = new ServerSocket(9999);
        //监听客户端连接
        Socket socket = serverSocket.accept();	//阻塞式监听，会一直等待客户端连接
        //获取输入流
        InputStream is = socket.getInputStream();
        //文件输出
        FileOutputStream fos = new FileOutputSteam(new File("receive.jpg"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len = is.read(buffer)) != -1) {
            fos.write(buffer, 0, len);
        }
        
        //通知客户端接收完毕
        OutputStream os = socket.getOutputStream();
        os.write("over".getBytes());
        
        //关闭资源
        fos.close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}

6 UDP

UDP没有客户端和服务端区分，这里只是方便显示

Copypublic class UdpClientDemo {
    public static void main(String[] args) throws Exception {
        //建立Socket
        DatagramSocket socket = new DatagramSocket();
        //建个包
        String msg = "test";
        InetAddress ip = InetAddress.getByName("127.0.0.1");
        int port = 9000;
        //数据，数据长度，接收方ip和端口
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, ip, port);
        //发送包
        socket.send(packet);
        //关闭资源
        socket.close();
    }
}
Copypublic class UdpServerDemo {
    public static void main(String[] args) {
        //开放端口
        DatagramSocket socket = new DatagramSocket(9000);
        //接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
        socket.receive(packet);
        System.out.println(new String(packet.getData(), 0, packet.getLength()));
        //关闭资源
        socket.close();
    }
}

7 UDP实现聊天

Copypublic class UdpSenderDemo {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(8888);
        //准备数据，控制台读取System.in
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String data = reader.readLine();
            byte[] datas = data.getBytes();
            DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress("127.0.0.1", 9999));
            socket.send(packet);
            
            if (data.trim().equals("bye")) {
                break;
            }
        }
        
        socket.close();
    }
}
Copypublic class UdpReceiveDemo {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9999);
        while (true) {
            //准备接收数据
            byte[] container = new byte[1024];
            DatagramPacket packet = new DatagramPacket(container, 0, container.length);
            socket.receive(packet);
            
            //断开连接
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);
            System.out.println(receiveData);
            
            if (receiveData.trim().equals("bye")) {
                break;
            }
        }
        
    }
}

如果要实现发送的同时可以接收信息，那么双方都要建立两个线程，一个负责发送，一个负责接收

8 URL

统一资源定位符

• 协议://ip地址:端口/项目名/资源

Copypublic class URLDemo {
    public static void main(String[] args) throws MalformedURLException {
        URL url = new URL("http://localhost:8080/test/index.html?a=1&b=2");
        System.out.println(url.getProtocol());	//协议
        System.out.println(url.getHost());	//主机ip
        System.out.println(url.getPort());	//端口
        System.out.println(url.getPath());	//文件
        System.out.println(url.getFile());	//全路径
        System.out.println(url.getQuery());	//参数
    }
}

利用URL下载网络资源

public class URLDownload {
    public static void main(String[] args) throws Exception {
        URL url = new URL("http://localhost:8080/test/test.txt");
        //连接到资源
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        
        InputStream is = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("receive.txt");
        
        byte[] buffer = new byte[1024];
        int len;
        while ((len = is.read(buffer)) != -1) {
            fos.write(buffer, 0, len);
        }
        
        fos.close();
        is.close();
        urlConnection.close();
    }
}