网络编程_学习笔记

1.网络通信的要素

1. 网络编程中有两个主要的问题

• 如何准确的定位到网络上的一台或多台主机
• 找到主机后如何进行通信

2. 网络编程中的要素

• ip 和端口号
• 网络通信协议 : udp tcp

3. 万物皆对象

2. IP

2.1 ip地址: InetAddress

• 唯一定位一台网络上的计算机

2.2 ip地址的分类

• ipv4/ipv6
  ipv4 : 127.0.0.1 ,4个字节组成;0~255,42亿 ~;30亿在北美,4亿在亚洲;2011年用尽;
  ipv6: 128位; 8个无符号整数;
• 公网(互联网)-私网(局域网)
  ABCD类地址
  192.168.xx.xx : 专门给组织内部使用的

2.3 域名

记忆ip问题

3. 端口

端口表示计算机上的一个程序的进程;

• 不同的进程有不同的端口号,用来区分软件
• 被规定 0~ 65535
• TCP,UDP : 单个协议下端口号不能冲突

端口号分类:

1. 共有端口 0~ 1023

HTTP: 80
HTTPS: 443
FTP：２1
Telent：23

2. 程序注册端口: 1024~ 49151,分配用户或者程序

Tomcat: 8080
MySQL: 3306
Oracle : 1521

3. 动态、私有 : 49152~ 65535
4. 常用的命令

netstat -ano  # 查看所有的端口
netstat -ano|findstr "端口号"  # 查看指定的端口
tasklist|findstr "端口号"   # 查看指定端口的进程

4. 通信协议

网络传输协议: 速率,传输码率,代码结构,传输控制…
TCP/IP协议簇: 实际上是一组协议

tcp: 用户传输协议
udp : 用户数据报协议
ip : 网络互连协议

TCP 和UDP 对比

TCP: 打电话

• 连接稳定
• 三次握手, 四次挥手
• 客户端,服务端
• 传输完成,释放连接,效率低

UDP: 发短信

• 不连接,不稳定
• 客户端,服务端 : 没有明确的界限
• 不管有没有准备好,都可以发送数据

4.1 TCP

客户端:

1. 连接服务器Socket
2. 发送消息

public class TcpClient {
    
    
    public static void main(String[] args) {
    
    
        Socket socket =null;
        OutputStream os =null;
        try {
    
    
            //1. 要知道服务器的地址,端口号
            InetAddress serverIP = InetAddress.getByName("127.0.0.1");
            int port =9999;
            //2. 创建一个socket连接
             socket = new Socket(serverIP, port);
            //3.发送消息IO流
             os = socket.getOutputStream();
            os.write("你好,java".getBytes());
        } catch (Exception e) {
    
    
            e.printStackTrace();
        } finally {
    
    
            //关闭资源(先开后关)
            if(socket!=null){
    
    
                try {
    
    
                    socket.close();
                } catch (IOException e) {
    
    
                    e.printStackTrace();
                }
            }
            if(os!=null){
    
    
                try {
    
    
                    os.close();
                } catch (IOException e) {
    
    
                    e.printStackTrace();
                }
            }
        }
    }
}

服务端

1. 建立服务的端口ServerSocket
2. 等待用户的链接 accept
3. 接收用户的消息

public class TcpServer {
    
    
    public static void main(String[] args) {
    
    
        ServerSocket serverSocket =null;
        Socket socket =null;
        InputStream is =null;
        ByteArrayOutputStream baos =null;
        try {
    
    
            //1. 我的有一个地址
           serverSocket = new ServerSocket(9999);
            //2. 等待客户端连接
            while (true){
    
    
                socket = serverSocket.accept();
                //3. 读取客户端的消息
                is = socket.getInputStream();
             /*
              byte[] buffer =  new byte[1024];
              int len;
              while ((len=is.read(buffer))!=-1){
                String msg = new String(buffer, 0, len);
                System.out.println(msg);
              }
              */
                //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(先开后关)
            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();
                }
            }
        }
    }
}

4.2 文件上传

public class TcpClient {
    
    
    public static void main(String[] args) throws Exception {
    
    
        //1. 穿件爱你一个Socket链接
        Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9000);
        //2. 创建一个输出流
        OutputStream os = socket.getOutputStream();
        //3. 读取文件
        FileInputStream fis = new FileInputStream(new File("a.png"));
        //4.写出文件
        byte[] buffer = new byte[1024];
        int len;
        while ((len=fis.read(buffer))!=-1){
    
    
            os.write(buffer,0,len);
        }
        //5 关闭资源
        fis.close();
        os.close();
        socket.close();
    }
}

public class TcpServer {
    
    
    public static void main(String[] args) throws IOException {
    
    
        //1 创建服务
        ServerSocket serverSocket = new ServerSocket(9000);
        //2. 监听客户端的链接
        Socket socket = serverSocket.accept();
        //3 获取输入流
        InputStream is = socket.getInputStream();
        //4 文件输出
        FileOutputStream fos = new FileOutputStream(new File("recive1.png"));
        byte[] buffer = new byte[1024];
        int len;
        while ((len=is.read(buffer))!=-1){
    
    
            fos.write(buffer,0,len);
        }
        //关闭资源
        fos.close();
        is.close();
        socket.close();
        serverSocket.close();
    }
}

4.3 UDP

不需要连接,需要知道对方的地址
发送消息:

//不需要连接服务器
public class UdpSend {
    
    
    public static void main(String[] args) throws IOException {
    
    
        //1 建立一个Socket
        DatagramSocket socket = new DatagramSocket();
        //2. 建个数据包
        String msg = "你好啊,udp";
        InetAddress ip = InetAddress.getByName("localhost");
        int port = 9090;
        // 数据,数据起始,数据长度,发给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, ip, port);

        //3 发送包
        socket.send(packet);
        //4 关闭流
        socket.close();
    }
}

接收消息:

//等待发送端的链接
public class UdpRecive {
    
    
    public static void main(String[] args) throws IOException {
    
    
        // 开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        // 接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
        socket.receive(packet);
        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(packet.getSocketAddress());

        System.out.println(new String(packet.getData(),0,packet.getLength()));
        System.out.println(new String(packet.getData(),0,packet.getData().length));
        //关闭连接
        socket.close();
    }
}

4.4 UDP聊天实现

发送方:

public class UdpSender {
    
    
    public static void main(String[] args) throws IOException {
    
    
        DatagramSocket socket = new DatagramSocket(8888);
        //准备数据  :控制台读取
        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("localhost",6666));
            socket.send(packet);
            if("bye".equals(data)){
    
    
                break;
            }
        }
        socket.close();

    }
}

接收方:

public class UdpReceive {
    
    
    public static void main(String[] args) throws IOException {
    
    
        DatagramSocket socket = new DatagramSocket(6666);
        while (true){
    
     //循环接收
            //准备接受包裹
            byte[] conrainer = new byte[1024];
            DatagramPacket packet = new DatagramPacket(conrainer,0,conrainer.length);
            socket.receive(packet); //阻塞式接收包裹
            //断开逻辑判断
            byte[] data = packet.getData();
            String receiveData = new String(data, 0, data.length);
            System.out.println(receiveData);
            System.out.println("bye".equals(receiveData));
            if("bye".equals(receiveData)){
    
    
                break;
            }
        }
        socket.close();
    }
}

4.5 多线程的聊天

发送端

public class TalkSend implements Runnable {
    
    
    DatagramSocket socket =null;
    BufferedReader reader =null;
    private int fromPort;
    private String toIP;
    private int toPort;

    public TalkSend(int fromPort, String toIP, int toPort) {
    
    
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;
        try {
    
    
            socket = new DatagramSocket(fromPort);
            //准备数据  :控制台读取
           reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (SocketException e) {
    
    
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
    
    
        while (true){
    
    
            try {
    
    
                String data = reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas, 0, datas.length, new InetSocketAddress(this.toIP,this.toPort));
                socket.send(packet);
                if("bye".equals(data)){
    
    
                    break;
                }
            }catch (Exception e){
    
    
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

接收端

public class TalkReceive implements Runnable {
    
    
    DatagramSocket socket =null;
    private int port;
    private String msgForm;

    public TalkReceive(int port,String msgForm) {
    
    
        this.port = port;
        this.msgForm=msgForm;
        try {
    
    
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
    
    
            e.printStackTrace();
        }
    }

    @Override
    public void run() {
    
    
        while (true){
    
     //循环接收
            try {
    
    
                //准备接受包裹
                byte[] conrainer = new byte[1024];
                DatagramPacket packet = new DatagramPacket(conrainer,0,conrainer.length);
                socket.receive(packet); //阻塞式接收包裹
                //断开逻辑判断
                byte[] data = packet.getData();
                String receiveData = new String(data, 0, data.length);
//                System.out.println(packet.getSocketAddress()+":"+packet.getPort()+"::"+receiveData);
                System.out.println(this.msgForm+":"+receiveData);
                if("bye".equals(receiveData)){
    
    
                    break;
                }
            } catch (IOException e) {
    
    
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

两个聊天端要分别开启发送和接收线程

//聊天1
public class TalkStudent {
    
    
    public static void main(String[] args) {
    
    
        new Thread(new TalkSend(8888,"localhost",9999)).start();
        new Thread(new TalkReceive(8889,"老师")).start();
    }
}
//聊天2
public class TalkTeacher {
    
    
    public static void main(String[] args) {
    
    
        new Thread(new TalkSend(9000,"localhost",8889)).start();
        new Thread(new TalkReceive(9999,"学生")).start();
    }
}

5. URL

https://www.baidu.com/
协议: // ip地址 : 端口/项目名/资源
统一资源定位符: 定位资源的,定位互联网上的某一个资源
下载网络资源的demo:

public class UrlDown {
    
    
    public static void main(String[] args) throws IOException {
    
    
        //1. 下载地址
        URL url = new URL(" https://m701.music.126.net/20210221231403/37cfc149e0a1bf7f76fa9066c27f1b77/jdyyaac/obj/w5rDlsOJwrLDjj7CmsOj/5001611989/2a8a/5d21/2db8/f1eee35c0d684e4e7d999368efaf56d9.m4a");
        //2. 连接到这个资源 http
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        InputStream is = urlConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("黄昏.m4a");
        byte[] buffer = new byte[1024];
        int len;
        while ((len=is.read(buffer))!=-1){
    
    
            fos.write(buffer,0,len);
        }
        fos.close();
        is.close();
        urlConnection.disconnect();
    }
}