13.网络编程
1.IP 地址
IP地址：InetAddress
import java.net.InetAddress;
import java.net.UnknownHostException;
//测试IP
public class TestInetAddress {
public static void main(String[] args) {
try {
//获取本机地址
InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
System.out.println(inetAddress1);
InetAddress inetAddress3 = InetAddress.getByName("localhost");
System.out.println(inetAddress3);
InetAddress inetAddress4 = InetAddress.getLocalHost();
System.out.println(inetAddress4);
//查询网站 IP 地址
InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");
System.out.println(inetAddress2);
//常用方法
//System.out.println(inetAddress2.getAddress());
System.out.println(inetAddress2.getCanonicalHostName());//规范的名字
System.out.println(inetAddress2.getHostAddress());//IP
System.out.println(inetAddress2.getHostName());//域名，或自己电脑的名字
} catch (UnknownHostException e) {
throw new RuntimeException(e);
}
}
}
2.端口
import java.net.InetSocketAddress;
public class TestSocketAddress {
public static void main(String[] args) {
InetSocketAddress socketAddress = new InetSocketAddress("127.0.0.1", 8080);
System.out.println(socketAddress);
System.out.println(socketAddress.getAddress());
System.out.println(socketAddress.getHostName());
System.out.println(socketAddress.getPort());
}
}
3.通信协议
4.TCP
客户端
- 连接服务器 Socket
- 发送消息
服务器
- 建立服务器的端口 ServerSocket
- 等待用户的连接 accept
- 接收用户的消息
例子：
客户端
import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
//客户端
public class TcpClientDemo01 {
public static void main(String[] args) throws Exception {
//1.创建一个 socket 连接
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("1.jpg"));
//4.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，我已经结束了
socket.shutdownOutput();//我已经传输完了
//确定服务器接收完毕，才能断开连接
InputStream inputStream = socket.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer2 = new byte[1024];
int len2;
while ((len2 = inputStream.read(buffer2)) != -1){
baos.write(buffer2, 0, len2);
}
//5.关闭连接
baos.close();
inputStream.close();
fis.close();
os.close();
socket.close();
}
}
服务器端
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
//服务端
public class TcpServerDemo01 {
public static void main(String[] args) throws Exception {
//1.创建服务
ServerSocket serverSocket = new ServerSocket(9000);
//2.监听客户端的连接
Socket socket = serverSocket.accept();//阻塞式监听，会一直等待客户端连接
//3.获取输入流
InputStream is = socket.getInputStream();
//4.文件输出
FileOutputStream fos = new FileOutputStream(new File("receive.jpg"));
byte[] buffer = new byte[1024];
int len;
while ((len = is.read(buffer)) != -1){
fos.write(buffer, 0, len);
}
//通知客户端我接收完毕了
OutputStream os = socket.getOutputStream();
os.write("我接收完毕了，你可以断开了".getBytes());
//5.关闭资源
fos.close();
is.close();
socket.close();
serverSocket.close();
}
}
5.UDP
不用连接，但需要直到对方的地址：Datagram
例1：消息发送
发送端
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，服务器";
//发送给谁
InetAddress localhost = InetAddress.getByName("localhost");
int port = 9090;
//数据，数据的长度起始，要发送给谁
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
import java.net.DatagramPacket;
import java.net.DatagramSocket;
//还是要等待客户端的连接
public class UdpServerDemo02 {
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);
socket.receive(packet);//阻塞接收
System.out.println(packet.getAddress().getHostAddress());
System.out.println(new String(packet.getData(), 0, packet.getLength()));
//关闭连接
socket.close();
}
}
例2：聊天实现
发送端
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
public class UdpSenderDemo01 {
public static void main(String[] args) throws IOException {
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("localhost", 6666));
socket.send(packet);
if (data.equals("bye")) break;
}
socket.close();
}
}
接收端
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class UdpReceiveDemo02 {
public static void main(String[] args) throws IOException {
DatagramSocket socket = new DatagramSocket(6666);
while (true){
//准备接收包裹
byte[] container = new byte[1024];
DatagramPacket packet = new DatagramPacket(container, 0, container.length);
socket.receive(packet);//阻塞式接收包裹
//断开连接 bye
byte[] data = packet.getData();
String receiveData = new String(data, 0, data.length);
System.out.println(receiveData);
if (receiveData.equals("bye")) break;
}
socket.close();
}
}
例3：UDP 多线程在线咨询
发送端
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;
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);
reader = new BufferedReader(new InputStreamReader(System.in));
} catch (SocketException e) {
throw new RuntimeException(e);
}
}
public TalkSend(DatagramSocket socket) {
this.socket = socket;
}
@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 (data.equals("bye")) break;
}catch (Exception e){
e.printStackTrace();
}
}
socket.close();
}
}
接收端
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
public class TalkReceive implements Runnable{
DatagramSocket socket = null;
private int port;
private String msgFrom;
public TalkReceive(int port, String msgFrom) {
this.port = port;
this.msgFrom = msgFrom;
try {
socket = new DatagramSocket(port);
} catch (SocketException e) {
throw new RuntimeException(e);
}
}
@Override
public void run() {
while (true){
try {
//准备接收包裹
byte[] container = new byte[1024];
DatagramPacket packet = new DatagramPacket(container, 0, container.length);
socket.receive(packet);//阻塞式接收包裹
//断开连接 bye
byte[] data = packet.getData();
String receiveData = new String(data, 0, data.length);
System.out.println(msgFrom + "：" + receiveData);
if (receiveData.equals("bye")) break;
} catch (IOException e) {
throw new RuntimeException(e);
}
}
socket.close();
}
}
学生端：
public class TalkStudent {
public static void main(String[] args) {
//开启两个线程
new Thread(new TalkSend(777, "localhost", 9999)).start();
new Thread(new TalkReceive(8888, "老师")).start();
}
}
老师端：
public class TalkTeacher {
public static void main(String[] args) {
new Thread(new TalkSend(5555, "localhost", 8888)).start();
new Thread(new TalkReceive(9999, "学生")).start();
}
}
6.URL 下载网络资源
url 使用：
import java.net.MalformedURLException;
import java.net.URL;
public class URLDemo {
public static void main(String[] args) throws MalformedURLException {
URL url = new URL("http://localhost:8080/helloworld/index.jsp?user=test&password=123");
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
}
}
下载网络资源：
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class URLDown {
public static void main(String[] args) throws IOException {
//1.下载地址
URL url = new URL("https://t7.baidu.com/it/u=1951548898,3927145&fm=193&f=GIF");
//2.连接到这个资源 HTTP
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = urlConnection.getInputStream();
FileOutputStream fos = new FileOutputStream("1.jpg");
byte[] buffer = new byte[1024];
int len;
while ((len = inputStream.read(buffer)) != -1) fos.write(buffer, 0, len);//写出这个数据
fos.close();
inputStream.close();
urlConnection.disconnect();//断开连接
}
}
