网络编程中的要素
- IP和端口号
- 网络通信协议
IP
ip地址:InteAddress
- 唯一定位一台网络计算机
- 127.0.0.1:本机localhost
IP地址的分类
-
IP地址分类
-
ipv4 / ipv6
- ipv4:127.0.0.1 ,4个字节组成
- ipv6:128位,8个无符号整数
-
公网(互联网)-私网(局域网)
- 192.168.xx.xxx,专门给组织内部使用的
- ABCD类地址
-
域名:记忆ip问题
package lesson01;
import java.net.InetAddress;
import java.net.UnknownHostException;
//测试IP
public class TestInteAddress {
public static void main(String[] args) {
try {
//查询本机地址
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);
//查询网址ip地址
InetAddress inetAddress4 = InetAddress.getByName("www.baidu.com");
System.out.println(inetAddress4);
//常用方法
System.out.println(inetAddress2.getCanonicalHostName());//规范的名字
System.out.println(inetAddress2.getHostAddress());//ip
System.out.println(inetAddress2.getHostName());//域名,或者自己电脑的名字
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
}
端口
端口表示计算机上的一个程序进程,不同的进程有不同的端口号!用来区分软件!
端口分类
-
公有端口0-1023
- HTTP:80
- HTTPS:443
- FTP:21
- Telent:23
-
程序注册端口:1024-49151,分配用户或者程序
- Tomcat:8080
- MySQl:3306
- Oracle:1521
-
动态、私有:49152-65535
package lesson01;
import java.net.InetSocketAddress;
public class TestInetSocketAddress {
public static void main(String[] args) {
InetSocketAddress socketAddress = new InetSocketAddress("127.0.0.1",8080);
System.out.println(socketAddress);// /127.0.0.1:8080
System.out.println(socketAddress.getAddress());// /127.0.0.1
System.out.println(socketAddress.getHostName());//127.0.0.1
System.out.println(socketAddress.getPort());//8080
}
}
通信协议
协议:约定,就好比我们现在说的是普通话
网络通信协议: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
出名的协议:
- TCP
- IP:网络互连协议
TCP UDP对比
TCP:打电话
-
连接,稳定
-
三次握手,四次挥手
最少需要三次,保证稳定连接! A:你愁啥? B:瞅你咋地? A:干一场! A:我要走了 B:你真的要走了吗? B:你真的真的要走了吗? A:我真的要走了!
-
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,都可以发给你
- 导弹
- DDOS:洪水攻击(饱和攻击)
客户端
- 连接服务器Socket
- 发送消息
package lesson02;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
//客户端
public class TcpClientDemo01 {
public static void main(String[] args) {
Socket socket = null;
OutputStream os =null;
try {
//1.要知道服务器的地址
InetAddress serverIP = InetAddress.getByName("127.0.0.1");
//2.端口号
int port = 9999;
//3.创建一个socket连接
socket = new Socket(serverIP,port);
//发送消息
os = socket.getOutputStream();
os.write("你好,欢迎!".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();
}
}
}
}
}
TCP实现聊天
服务器
- 建立服务的端口ServerSocket
- 等待用户的链接accept
- 接收用户的消息
package lesson02;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
//服务端
public class TcpServerDemo01 {
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
InputStream is = null;
ByteArrayOutputStream baos = null;
try {
//1.我得有一个地址
serverSocket = new ServerSocket(9999);
//2.等待客户端连接过来
socket = serverSocket.accept();
//3.读取客户端的消息
is = socket.getInputStream();
//管通道
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();
}
}
}
}
}
UDP消息发送
发短信:不用连接,需要知道对方的地址
发送消息
发送端
package lesson02;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
//不需要连接服务器
public class udpClientDemo01 {
public static void main(String[] args) throws Exception {
//1.建立一个Socket
DatagramSocket socket = new DatagramSocket();
//2.建个包
String msg = "你好!";
InetAddress localhost = InetAddress.getByName("localhost");
int port = 9090;
//数据,数据的长度起始,发送给谁
DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);
//3.发送包
socket.send(packet);
//4.关闭流
socket.close();
}
}
接收端
package lesson02;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
//还是要等待客户端的连接!
public class udpServerDemo01 {
public static void main(String[] args) throws Exception {
//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);//接收
socket.receive(packet);
System.out.println(packet.getAddress().getHostAddress());
System.out.println(new String(packet.getData(),0,packet.getLength()));
//关闭连接
socket.close();
}
}
URL
统一资源定位符:定位资源的,定位互联网上的某一个资源
URL下载网络资源
package lesson02;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class URLDowm {
public static void main(String[] args) throws Exception {
//1.下载地址
URL url = new URL("http://www.4kbizhi.com/d/file/2021/01/27/small1215008dzj01611720900.jpg");
//2.连接到这个资源 HTTP
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = urlConnection.getInputStream();
FileOutputStream fos = new FileOutputStream("SecurityFile2.jpg");
byte[] bytes = new byte[1024];
int len;
while ((len = inputStream.read(bytes)) != -1){
fos.write(bytes,0,len);//写出这个数据
}
fos.close();
inputStream.close();
urlConnection.disconnect();//断开连接
}
}