java网络编程

Java网络编程

网络编程也称套接字编程
网络通信=套接字通信，即socket
socket 套接字，插座
ip 指地址每台计算机地址要不同
端口指进程端口号每个计算机的进程的端口号要不同
TCP 类似两者打电话，要先建立连接，建立连接要3次握手4次挥手，一般是客户端和服务端
UDP 类似发短信，不用连接，直接发，另一边可以自己去收，可能会出现丢包，一般是客户端之间
tcp麻烦但不宜丢包 udp简单但容易丢包

回车和换行的区别

回车enter 硬回车，段落直接换行，表示段落结束

换行CTRL+enter或者shift+enter软回车，只是光标下移，表示段落未结束

TCP
客户端
1. socket 通过端口和ip建立连接
2. os.write 发消息
服务端
1. serversocket 建立进程端口
2. accept 监听等待用户连接，返回客户端socket
3. 接受用户消息
  1. byte[1024] is.read(bytes)缓存区，存读取数据到bytes中
  2. byteArrayOutPutStream，baos.write(bytes,0,length)，写数据到bos中，防止中文太长越界
  3. bos.toString()，读取客户端数据，输出
io流
客户端 socket.getoutputstream os.write 往外写东西
服务端 serversocket.getinputstream is.read(new byte[1024])读is到数组bytes中
接收文件就用文件管道流，接收字符串就用字符串管道流

接收格式对应输出内容的格式

//接收文件，文件管道流接收
FileOutputStream fos = new FileOutputStream(new File("receive2.jpg"));

byte[] buffer = new byte[1024];
int len;
while ((len=is.read(buffer))!=-1){
    //写入fos
    fos.write(buffer,0,len);
}

//接收字符串，字符串管道流接收（字节数组）
ByteArrayOutputStream baos = new ByteArrayOutputStream();

byte[] buffer2 = new byte[1024];
int len2;
while ((len2=is.read(buffer2))!=-1){
    //写入baos
    baos.write(buffer2,0,len2);
}
//转换成字符串并输出
System.out.println(baos.toString());

文件传输过程

将file变为fis->fis.read(clbuffer)fis读出文件->文件数据存入clbuffer->os.write(clbuffer,0,len)->将clbuffer写入os

is.read(sebuffer) is读出os写入的数据->数据存入sebuffer->fos.write(sebuffer,0,len)->将sebuffer写入fos->fos变为file

is os对应，拥有相同数据

UDP
分为发送端和接收端，没有客户服务器的区分，两者可以同时是发送和接收

发送端

建立socket

DatagramSocket socket = new DatagramSocket();

建立包
port为目标端口

DatagramPacket datagramPacket = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);

发送包
```
socket.send(datagramPacket);
```

接收方

建立对应socket，要定义接收方端口，和发送方对应

创建数组建立包

DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);

接收包

socke.receive(packet);
System.out.println(new String(packet.getData(),0,packet.getLength()));

控制台输入

//接收控制台输入
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
String msg = bufferedReader.readLine();

UDP多线程在线咨询

多线程要实现Runnable接口

public class TalkSend implements Runnable{
    DatagramSocket socket = null;
    BufferedReader bufferedReader = null;

    private int fromPort;
    private int toPort;
    private String toIp;

    public TalkSend(int fromPort, int toPort, String toIp) {
        //发送方端口；目的端口；目的人地址
        this.fromPort = fromPort;
        this.toPort = toPort;
        this.toIp = toIp;
        try {
            //需要接收的端口
            socket = new DatagramSocket(fromPort);
            bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

public class TalkReceive implements Runnable{

    // 接收端口（=toPort）；发送人名称
    DatagramSocket socket = null;
    private int port;
    private String msgFromName;

    public TalkReceive(int port,String msgFromName) {
        this.port = port;
        this.msgFromName = msgFromName;
        try {
            socket = new DatagramSocket(port);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

重写run方法，实现发送消息

@Override
public void run() {
    while (true){
        try {
            String msg = bufferedReader.readLine();
            byte[] bytes = msg.getBytes();
            DatagramPacket packet = new DatagramPacket(bytes,0,bytes.length, new InetSocketAddress(toIp,toPort));
            socket.send(packet);
            if (msg.equals("end")) break;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
    socket.close();
}
@Override
    public void run() {
        while (true){
            try {
                byte[] bytes = new byte[1024];
                DatagramPacket packet = new DatagramPacket(bytes,0,bytes.length);
                socket.receive(packet);
                byte[] data = packet.getData();
                String s = new String(data, 0, packet.getLength());
                System.out.println(msgFromName+":"+s);
                if (s.equals("end")) break;
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        socket.close();
    }

创建线程，调用start()方法，start调用run方法

public static void main(String[] args) {
    new Thread(new TalkSend(5555,9999,"localhost")).start();
    new Thread(new TalkReceive(8888,"学生")).start();
}

public static void main(String[] args) {
    new Thread(new TalkSend(7777,8888,"localhost")).start();
    new Thread(new TalkReceive(9999,"老师")).start();
}

URL
http://www.baidu.com
统一资源定位符，定位互联网某一个资源
域名www.baidu.com，ip 127.0.0.1
域名解析是把域名解析为ip，域名为了好记

五部分组成，可以少不能多

协议://ip地址:端口/项目/资源

public class URLDemo01 {
    public static void main(String[] args) throws MalformedURLException {
        URL url = new URL("https://localhost:8080/helloworld/index.jsp?username=kuangshen&password=123");
        System.out.println(url.getProtocol());//协议
        System.out.println(url.getHost());//ip
        System.out.println(url.getPort());//端口
        System.out.println(url.getPath());//文件（项目）
        System.out.println(url.getFile());//文件全路径
        System.out.println(url.getQuery());//参数
    }
}

    /*子类引用指向父类对象，不对
    父类引用指向子类对象，对
    我的理解是，右边代表实际大小，先创建，左边为引用
    子类继承父类，所以子类占用空间更大
    父类创建大小不够，就不行*/
    Student student1 = new People();

public class URLDown {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://m10.music.126.net/20241104151656/39a2f4723d44fb7ba51813c995098ea8/yyaac/obj/wonDkMOGw6XDiTHCmMOi/2849745486/65c1/cb3b/e14e/67d13b0595b4313864e163c1db69cf7d.m4a?vuutv=vFr1k2kmyFwuOdGKS9tf9hhF0kjDp9zfMnuD6Ow7wMdsGgxGuI59WNe7IVST5jgIp1mxAIcrn6dTXb9fd/Txz5u1nhDGtKdpXKJEA5hhV0E=");
        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
        InputStream is = httpURLConnection.getInputStream();
        FileOutputStream fos = new FileOutputStream("hell.m4a");
        byte[] buffer = new byte[1024];
        int len;
        while ((len=is.read(buffer))!=-1){
            fos.write(buffer,0,len);
        }
        fos.close();
        is.close();
        httpURLConnection.disconnect();
    }
}

posted @ 2025-04-22 22:07 学习java的白菜阅读(15) 评论(0) 收藏举报

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