Java网络编程
一.网络通信的要素
- 通信双方的地址：
- ip地址
- 端口号
- 网络通信协议
IP
ip地址对应java的类：InetAddress
- 唯一定位一台网络上计算机
- 127.0.0.1 本机地址localhost
- IP地址的分类：
- ipv4 127.0.0.1.四个字节(32位)组成，42亿
- ipv6 16个字节（128位）组成
- 公网（互联网）-私网（局域网）
- 域名：记忆IP问题
package test;
import java.net.InetAddress;
public class file {
public static void main(String[] args) throws Exception{
//查询网站ip地址
InetAddress inetAddress1=InetAddress.getByName("www.baidu.com");
//查询本机ip地址
InetAddress inetAddress2=InetAddress.getByName("localhost");
InetAddress inetAddress3=InetAddress.getLocalHost();
System.out.println(inetAddress1);
System.out.println(inetAddress2);
System.out.println(inetAddress3);
//常用方法
System.out.println(inetAddress1.getAddress());
System.out.println(inetAddress1.getCanonicalHostName());//规范的名字,ip
System.out.println(inetAddress1.getHostAddress());//ip
System.out.println(inetAddress1.getHostName());//域名
}
}
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
- 规定为0-65535
- 分为TCP和UDP端口（65535*2）；单个协议下端口号不能冲突
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
netstart -ano查看所有端口
netstart -ano|findstr "5900"查看指定的端口
tasklist|findstr "8696"查看指定端口的进程
package test;
import java.net.InetSocketAddress;
public class file {
public static void main(String[] args) throws Exception{
InetSocketAddress inetSocketAddress=new InetSocketAddress("127.0.0.1",8000);
System.out.println(inetSocketAddress);
//获取主机名
System.out.println(inetSocketAddress.getAddress());
System.out.println(inetSocketAddress.getHostName());
System.out.println(inetSocketAddress.getHostString());
//获取端口号
System.out.println(inetSocketAddress.getPort());
}
}
通信协议
TCP/IP协议簇
TCP：用户传输协议
UDP：用户数据报协议
IP：网络互连协议
TCP vs UDP
TCP：打电话
- 连接，稳定
- 三次握手四次挥手
- 最少需要3次，保证稳定连接
- 客户端，服务端
- 传输完成，释放连接，效率低
UDP：发消息 - 不连接，不稳定
- 客户端，服务端：没有明确的界限
- DDOS（饱和攻击）
TCP
客户端
- 链接服务器Socket
- 发送消息
package oop;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class Client {
public static void main(String[] args) throws Exception{
Socket socket=null;
OutputStream os=null;
try{
//1.要知道服务器地址,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);
//发送消息
os=socket.getOutputStream();
os.write("你好".getBytes());
}catch(
UnknownHostException e)
{
e.printStackTrace();
}finally{
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
- 建立服务的端口ServerSocket
- 等待用户的连接accept
- 接收用户的消息
package oop;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
ByteArrayOutputStream baos = null;
InputStream ins = null;
try {
//要有一个地址
serverSocket = new ServerSocket(9999);
//等待客户端连接
socket = serverSocket.accept();
//读取客户端消息
ins = socket.getInputStream();
//管道流
baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len;
while ((len = ins.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 (ins != null) {
try {
ins.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
发送消息
- 发送端
package oop;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class Client {
public static void main(String[] args) throws Exception {
//1.建立一个Socket
DatagramSocket datagramSocket=new DatagramSocket();
//2.建个包
String msg="hello world";
InetAddress localhost=InetAddress.getByName("127.0.0.1");
int port=9000;
DatagramPacket datagramPacket= new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);
//3.发送包
datagramSocket.send(datagramPacket);
//关闭流
datagramSocket.close();
}
}
- 接收端
package oop;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class Server {
public static void main(String[] args) throws Exception {
//开放端口
DatagramSocket datagramSocket=new DatagramSocket(9000);
//接收数据包
byte[] buffer=new byte[1024];
DatagramPacket datagramPacket=new DatagramPacket(buffer,0,buffer.length);
datagramSocket.receive(datagramPacket);
//关闭
datagramSocket.close();
System.out.println(new String(datagramPacket.getData(),0,datagramPacket.getLength()));
}
}
二.URL
统一资源定位符：定位互联网上的某一个资源
格式：协议://ip地址:端口好//项目名//资源
连接URL，下载资源
package oop;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class Test2 {
public static void main(String[] args) throws Exception {
URL url=new URL("https://www.bilibili.com/video/BV1LJ411z7vY?p=12");
//获取协议
System.out.println(url.getProtocol());
//获取主机
System.out.println(url.getHost());
//获取文件
System.out.println(url.getPath());
//获取文件全路径
System.out.println(url.getFile());
//获取参数
System.out.println(url.getQuery());
HttpURLConnection httpURLConnection=(HttpURLConnection) new url.openConnection();
InputStream inputStream=httpURLConnection.getInputStream();
FileOutputStream fos=new FileOutputStream("f.mp4");
byte[] buffer=new byte[1024];
int len;
while((len=inputStream.read(buffer))!=-1){
fos.write(buffer,0,len);
}
fos.close();
inputStream.close();
httpURLConnection.disconnect();
}
}