这里仅对于java编程所需要用到的网络编程知识进行讲解,想要学习网络编程更深入部分推荐学习《计算机网络》
计算机网络:
网络编程:
IP地址:
端口:
协议:
IP地址:网络中设备的唯一标识
IP地址分为两个大类:
IP地址常用查询命令:(应用于命令cmd中)
ipconfig:查看本机IP地址
ping IP地址:检查网络是否连通
再介绍一个特殊IP地址:
127.0.0.1:代表本机地址,一般拿来测试
端口:设备上应用程序的唯一标识
端口号:用两个字节标识的整数,它的取值范围在065535之间。其中01023之间的端口号一般用于知名网络服务和应用,普通的应用程序一般使用1024以上的端口号。当一个端口号被占用,会导致当前程序启动失败
协议:计算机网络中,连接和通信的规则被称为网络通信协议
UDP协议:
TCP协议:
为了方便我们对IP地址的获取和操作,java提供了InetAddress类供我们使用
InetAddress:此类标识Internet协议地址
方法名 | 说明 |
---|---|
static InetAddress getByName(String host) | 确定主机名称的IP地址;host可以是机器名,可以是IP地址 |
String getHostName() | 获得此IP地址的主机名 |
String getHostAddress() | 获得此IP地址字符串 |
下面给出示例代码:
import java.net.InetAddress;
import java.net.UnknownHostException;
public class Demo1 {
public static void main(String[] args) throws UnknownHostException {
//采用static方法确认主机名称IP地址(这里可以是机器名DESKTOP-IHG93KD或者IP地址192.168.31.129)
InetAddress inetAddresses1 = InetAddress.getByName("DESKTOP-IHG93KD");
//获得该IP地址的主机名
String name = inetAddresses1.getHostName();
System.out.println(name);
//获得IP地址字符串
String ip = inetAddresses1.getHostAddress();
System.out.println(ip);
}
}
UDP通信原理:
UDP发送数据步骤:
下面给出代码示例:
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class Demo2 {
public static void main(String[] args) throws Exception{
//创造发送端Socket对象(DatagramSocket)
DatagramSocket ds = new DatagramSocket();
//创造数据,并把数据打包
//(DatagramPacket dp = new DatagramPacket(byte[] bys,int length,InetAddress address,int port ))
//依次需要:发送包内容(byte形式),长度,传输IP地址,传输端口
byte[] bys = "Hello,UDP".getBytes();
int len = bys.length;
InetAddress address = InetAddress.getByName("DESKTOP-IHG93KD");
int port = 10086;
DatagramPacket dp = new DatagramPacket(bys,len,address,port);
//可以简化为:(bys,bys.length,InetAddress.getByName("DESKTOP-IHG93KD"),10086);
//通过发送端对象,发送数据包对象
ds.send(dp);
//关闭发送端
ds.close();
}
}
UDP接收数据步骤:
下面给出代码示例:
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class Demo3 {
public static void main(String[] args) throws IOException {
//创造接收方对象(DatagramSocket),注意:这里需要匹配之前的端口,所以需要标注端口10086
DatagramSocket ds = new DatagramSocket(10086);
//创造数据,并打包
byte[] bys = new byte[1024];
int len = bys.length;
//这里需要一个数据接收byte和长度即可(这里的0是起始点)
DatagramPacket dp = new DatagramPacket(bys,0,len);
//调用Socket方法来接收
ds.receive(dp);
//接收后打印出来
byte[] data = dp.getData();
int length = dp.getLength();
String s = new String(data,0,length);
System.out.println(s);
//以上均可简写为:System.out.println(new String(dp.getData(),0,dp.getLength()));
//释放资源
ds.close();
}
}
要求:
代码如下:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class Send {
public static void main(String[] args) throws Exception{
//首先创建Socket对象,作为发送端
DatagramSocket ds = new DatagramSocket();
//这里我们采用BR字符串缓冲流来输入数据
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String line;
while ((line = br.readLine())!=null){
//如果是886,我们退出程序
if("886".equals(line)){
break;
}
//如果不是886,我们封装数据并发送
byte[] bytes = line.getBytes();
int len = bytes.length;
DatagramPacket dp = new DatagramPacket(bytes,0,len, InetAddress.getByName("DESKTOP-IHG93KD"),12345);
ds.send(dp);
}
//最后释放资源
ds.close();
}
}
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class Receive {
public static void main(String[] args) throws IOException {
//创造接收方对象(DatagramSocket),注意:这里需要匹配之前的端口,所以需要标注端口12345
DatagramSocket ds = new DatagramSocket(12345);
//采用死循环接收
while (true){
//创造数据,并打包
byte[] bys = new byte[1024];
int len = bys.length;
DatagramPacket dp = new DatagramPacket(bys,0,len);
//调用Socket方法来接收
ds.receive(dp);
//接收后打印出来
System.out.println(new String(dp.getData(),0,dp.getLength()));
}
}
}
TCP通信协议是一种可靠的网络协议,它在通信的两端各建立一个Socket对象,从而在通信的两端形成网络虚拟链路
一旦建立了虚拟的网络链路,两端的程序就可以通过虚拟链路进行通信
Java对基于TCP协议的网络提供了良好的封装,使用Socket对象来代表两端的通信端口,并通过Socket产生IO流来进行网络通信
Java为客户端提供了Socket类,为服务器端提供了ServerSocket类
TCP发送数据步骤:
下面给出代码示例:
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
public class Demo1 {
public static void main(String[] args) throws IOException {
//首先创建发送方对象Socket(这里使用Socket类)
//Socket有两种创建方法
//第一种:Socket(String IP地址号,端口号)
Socket s = new Socket("192.168.31.129",12345);
//第二种:Socket(InetAddress,端口号)
//Socket ss = new Socket(new InetAddress("DESKTOP-IHG93KD"),10000)
//获得输出流并写数据
//我们可以使用Socket方法
OutputStream os = s.getOutputStream();
os.write("Hello,world".getBytes());
//最后释放资源
s.close();
}
}
TCP接收数据步骤:
下面给出代码示例:
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Demo2 {
public static void main(String[] args) throws IOException {
//首先创建服务器端的Socket(采用ServerSocket类)
//这里需用一种构造方法:ServerSocket(int port);
ServerSocket ss = new ServerSocket(12345);
//我们需要接收ss所对接的Socket,
Socket s = ss.accept();
//然后我们通过Socket类来创建输入流接收数据
InputStream is = s.getInputStream();
byte[] bys = new byte[1024];
int len = is.read(bys);
System.out.println(new String(bys,0,len));
//最后释放资源
s.close();
ss.close();
}
}
练习1:
下面给出示例代码:
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
public class ClientDemo {
public static void main(String[] args) throws IOException {
//第一步,创建客户端Socket对象
Socket s = new Socket("192.168.31.129",10086);
//第二步,发送数据
OutputStream os = s.getOutputStream();
os.write("我已经给你传输了数据".getBytes());
//第三步,接受反馈
InputStream is = s.getInputStream();
byte[] bys = new byte[1024];
int len;
while ((len = is.read(bys)) != -1) {
System.out.println(new String(bys, 0, len));
}
//释放资源(这里直接释放Socket对象,由Socket对象创建的其他对象也释放)
s.close();
}
}
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class RerverDemo {
public static void main(String[] args) throws IOException {
//第一步,创建服务端Socket对象(ServerSocket)
ServerSocket ss = new ServerSocket(10086);
//第二步,监听客户端
Socket s = ss.accept();
//第三步,创建输入流接收数据
InputStream is = s.getInputStream();
byte[] bys = new byte[1024];
int len;
while ((len = is.read(bys)) != -1) {
System.out.println(new String(bys, 0, len));
}
//第四步,给出反馈
OutputStream os = s.getOutputStream();
os.write("我已经收到了数据".getBytes());
//释放资源
ss.close();
}
}
练习2:
下面给出代码示例:
import java.io.*;
import java.net.Socket;
public class ClientDemo {
public static void main(String[] args) throws IOException {
//创建对象
Socket s = new Socket("192.168.31.129",11111);
//从键盘输入,因此封装BR对象
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//采用字符流输出,封装BW对象
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
//开始输入
String line;
while ((line = br.readLine()) != null){
//如果为886,退出
if("886".equals(line)){
break;
}
//如果不是,采用字符流输出
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
br.close();
bw.close();
s.close();
}
}
public class ServerDemo {
public static void main(String[] args) throws IOException {
//创造对象
ServerSocket ss = new ServerSocket(11111);
//监听客户端
Socket s = ss.accept();
//我们采用缓冲字符流输入流接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
String line;
while ((line = br.readLine()) != null){
System.out.println(line);
}
//释放资源
ss.close();
}
}
练习3:
下面给出代码示例:
import java.io.*;
import java.net.Socket;
public class ClientDemo {
public static void main(String[] args) throws IOException {
//创建对象
Socket s = new Socket("192.168.31.129",10086);
//从键盘输入,因此封装BR对象
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//采用字符流输出,封装BW对象
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
//开始输入
String line;
while ((line = br.readLine()) != null){
//如果为886,退出
if("886".equals(line)){
break;
}
//如果不是,采用字符流输出
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
s.close();
}
}
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo {
public static void main(String[] args) throws IOException {
//创建对象
ServerSocket ss = new ServerSocket(10086);
//监听
Socket s = ss.accept();
//创建BR接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
//创建BW写入文件
BufferedWriter bw = new BufferedWriter(new FileWriter("E:\\编程内容\\javaSE\\网络编程\\Class\\src\\Text2\\s.txt"));
//开始循环写入
String line;
while ((line = br.readLine()) != null){
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
ss.close();
bw.close();
}
}
练习4:
下面给出示例代码:
import java.io.*;
import java.net.Socket;
public class ClientDemo {
public static void main(String[] args) throws IOException {
//创建对象
Socket s = new Socket("192.168.31.129",10086);
//封装文本文件数据
BufferedReader br = new BufferedReader(new FileReader("E:\\编程内容\\javaSE\\网络编程\\Class\\src\\Text2\\s.txt"));
//封装写入数据
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
//循环
String line;
while ((line = br.readLine()) != null){
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
s.close();
br.close();
}
}
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo {
public static void main(String[] args) throws IOException {
//创建对象
ServerSocket ss = new ServerSocket(10086);
//监听
Socket s = ss.accept();
//创建BR接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
//创建BW写入文件
BufferedWriter bw = new BufferedWriter(new FileWriter("E:\\编程内容\\javaSE\\网络编程\\Class\\src\\Text3\\s.txt"));
//开始循环写入
String line;
while ((line = br.readLine()) != null){
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
ss.close();
bw.close();
}
}
练习5:
下面给出示例代码:
import java.io.*;
import java.net.Socket;
public class clientDemo {
public static void main(String[] args) throws IOException {
//创建对象
Socket s = new Socket("192.168.31.129",10086);
//封装文本文件数据
BufferedReader br = new BufferedReader(new FileReader("E:\\编程内容\\javaSE\\网络编程\\Class\\src\\Text2\\s.txt"));
//封装写入数据
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
//循环
String line;
while ((line = br.readLine()) != null){
bw.write(line);
bw.newLine();
bw.flush();
}
// {
// //自定义结束标记
// bw.write("886");
// bw.newLine();
// bw.flush();
// }
//或者采用Socket固有方法(表示输出结束)
s.shutdownOutput();
//接受反馈
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(s.getInputStream()));
String data = bufferedReader.readLine();
System.out.println("服务器的反馈:" + data);
//释放资源
s.close();
br.close();
}
}
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo {
public static void main(String[] args) throws IOException {
//创建对象
ServerSocket ss = new ServerSocket(10086);
//监听
Socket s = ss.accept();
//创建BR接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
//创建BW写入文件
BufferedWriter bw = new BufferedWriter(new FileWriter("E:\\编程内容\\javaSE\\网络编程\\Class\\src\\Text4\\s.txt"));
//开始循环写入
String line;
while ((line = br.readLine()) != null){
// if("886".equals(line)){
// break;
// }
bw.write(line);
bw.newLine();
bw.flush();
}
//给出反馈
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
bufferedWriter.write("文件上传成功");
bufferedWriter.newLine();
bufferedWriter.flush();
//释放资源
ss.close();
bw.close();
}
}
好的,关于网络编程的知识我们讲解到这里