计算机网络
网络编程
IP地址
端口
协议
IP地址: 是网络中设备的唯一标识
IP地址分为两大类
DOS常用命令:
特殊IP地址
InetAddress:此类表示Internet协议(IP)地址
package com.itdemo_28;
import java.net.InetAddress;
import java.net.UnknownHostException;
public class InnetAddressDemo {
public static void main(String[] args) throws UnknownHostException {
// static InetAddress getByName(String host)确定主机名称的IP地址。主机名称可以是机器名称,也可以 是IP地址
// InetAddress address = InetAddress.getByName("LAPTOP-LT5KV2ED");
InetAddress address = InetAddress.getByName("192.168.124.9");
// String getHostName() 获取此IP地址的主机名
String name = address.getHostName();
// String getHostAddress() 返回文本显示中的IP地址字符串
String ip = address.getHostAddress();
System.out.println("主机名"+name);
System.out.println("IP地址"+ip);
}
}
端口: 设备上应用程序的唯一标识
端口号: 用两个字节表示的整数,它的取值范围是0-65535. 其中,0-1023之间的端口号用于一些知名的网络服务和应用,普通的应用程序需要使用1024以上的端口号,如果端口号被另一个服务或应用占用,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
- 用户数据报协议(User Datagram Protocol)
- UDP是无连接通信协议,即在数据传输时,数据的发送端和接收端不建立逻辑连接,简单来说,当一台计算机向另外一台计算机发送数据时,发送端不确认接收端是否存在,就会发出数据,同样接收端在收到数据时,也不会向发送端反馈是否接收到数据
- 由于使用UDP协议消耗资源小,通信效率高,所以通常会用于音频,视频,和普通数据的传输
- 例如视频会议通常采用UDP协议,因为这种情况即使偶尔丢失一两个数据包,也不会对接收结果产生太大影响,但是在使用UDP协议传送数据时,由于UDP的面向无连接性,因此在传输重要数据时不建议使用UDP协议
TCP协议
传输控制协议(Transmission Control Protocol)
TCP协议是面向连接的通信协议,既传输数据之前,在发送端和接收端建立逻辑连接,然后再传输数据,它提供了两台计算机之间可靠无差别的数据传输,在TCP连接中必须明确客户端与服务器端,由客户端向服务器端发出连接请求,每次连接的创建都需要经过"三次握手";
三次握手: TCP协议中,在发送数据的准备阶段,客户端与服务器之间的三次交互,以保证连接的可靠
第一次握手,客户端向服务器端发出连接请求,等待服务器确认
第二次握手,服务器端向客户端回送一个响应,通知客户端收到了连接请求
第三次握手,客户端再次向服务器端发送确认信息,确认连接
完成三次握手,连接建立后,客户端和服务器就可以开始进行数据传输了,由于这种面向连接的特性
TCP协议可以保证传输数据的安全,所以应用十分广泛,例如上传文件,下载文件,浏览网页等.
发送数据的步骤
package com.itdemo_28;
import java.io.IOException;
import java.net.*;
public class SendDemo {
public static void main(String[] args) throws IOException {
// 创建发送端的Socket对象(DatagramSocket)
//DatagramSocket() 构造数据报套接字并将其绑定到本地主机上的任何可用端口。
DatagramSocket ds = new DatagramSocket();
//创建数据,并把数据打包
//DatagramPacket(byte[] buf, int length, InetAddress address, int port)
// 构造一个数据包,发送长度为 length的数据包到指定主机上的指定端口号。
byte[] bys = "hello,udp,我来了".getBytes();
// int length = bys.length;
// InetAddress address = InetAddress.getByName("192.168.124.9");
// int port =10086;
// DatagramPacket dp = new DatagramPacket(bys,length,address,port);
DatagramPacket dp = new DatagramPacket(bys,bys.length,InetAddress.getByName("192.168.124.9"),10086);
//调用DatagramSocket对象的方法发送数据
//void send (DatagramSocket p) 从此套接字发送数据报包
ds.send(dp);
//关闭发送数据
// void close() 关闭此数据报套接字
ds.close();
}
}
发送数据的步骤
接收数据的步骤
package com.itdemo_28;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
public class ReceiveDemo {
public static void main(String[] args) throws IOException {
//创建接收端的Socket对象(DatagramSocket)
//DatagramSocket (int port)构造数据报套接字并将其绑定到本地主机上的指定接口
DatagramSocket ds = new DatagramSocket(10086);
//创建一个数据包,用于接收数据
// DatagramPacket (byte[] bys ,int length) 构造一个DatagramPacket用于接收长度为length数据包
byte[] bys =new byte[1024];
DatagramPacket dp = new DatagramPacket(bys,bys.length);
//调用DatagramSocket对象的方法接收数据
ds.receive(dp);
//解析数据包,并把数据在控制台显示
//byte[] getData() 返回数据缓冲区
// byte[] datas = dp.getData();//拿到的是数据缓冲区
// //int getlength() 返回要发送的数据的长度或接收道德数据的长度
// int len =dp.getLength();//实际发送多少数据
// String dataString = new String(datas,0,len);
// System.out.println("数据是:"+dataString);
//可优化为
System.out.println("数据是: "+new String(dp.getData(),0,dp.getLength()));
//关闭接收数据
ds.close();
}
}
接收数据的步骤
按照下面的要求实现程序
发送端
package com.itdemo_28;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
public class SendTest {
public static void main(String[] args) throws IOException {
//创建发送端Socket对象
DatagramSocket ds = new DatagramSocket();
//自己封装,键盘录入
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String line;
while ((line=br.readLine())!=null){
//输入的数据是886,发送数据结束
if ("886".equals(line)){
break;
}
//创建数据,并把数据打包
byte[] bys = line.getBytes();
DatagramPacket dp = new DatagramPacket(bys,bys.length,InetAddress.getByName("192.168.124.9"),12345);
//调用DatagramSocket对象的发送数据
ds.send(dp);
}
//关闭发送端
ds.close();
}
}
接收端
package com.itdemo_28;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
public class ReceiveTest {
public static void main(String[] args) throws IOException {
//创建接收端Socket对象(DatagramSocket
DatagramSocket ds = new DatagramSocket(12345);
while(true){
//创建一个数据包,用于接收数据
byte[] bys = new byte[1024];
DatagramPacket dp = new DatagramPacket(bys,bys.length);
//调用DatagramSocket对象的方法接收数据
ds.receive(dp);
System.out.println("数据是: "+new String(dp.getData(),0,dp.getLength()));
}
//关闭接收端
// ds.close();
}
}
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接口,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
发送数据的步骤
package com.itdemo_28;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class ClientDemo {
public static void main(String[] args) throws IOException {
//创建客户端Socket对象
//Socket(String host,int port) 创建流套接字并将其连接到指定主机上的指定端口
// Socket s = new Socket(InetAddress.getByName("192.168.124.9"),10000);
Socket s = new Socket("192.168.124.9",10000);
//获取输出流,写数据
//OutputStream getOutputStream() 返回此套接字的输出流
OutputStream os = s.getOutputStream();
os.write("hello,tcp,我来了".getBytes());
//释放资源
s.close();
}
}
接收数据的步骤
package com.itdemo_28;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo {
public static void main(String[] args) throws IOException {
//创建服务器端的Socket对象
//ServerSocket(int port)创建绑定到指定端口的服务器套接字
ServerSocket ss = new ServerSocket(10086);
//Socket accept ()侦听要连接到此套接字并接受它
Socket s = ss.accept();
//获取输入流, 读数据,并把数据显示在控制台
InputStream is = s.getInputStream();
byte[] bys = new byte[1024];
int len = is.read(bys);
String data = new String(bys,0,len);
System.out.println("数据是: " +data);
//释放资源
s.close();
ss.close();
}
}
练习1
案例分析
服务器端
package com.itdemo_28;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo01 {
public static void main(String[] args) throws IOException {
//创建服务器端的Socket对象
ServerSocket ss = new ServerSocket(10086);
//监听客户端连接,返回Socket对象
Socket s = ss.accept();
//获取输入流,读数据,并显示在控制台
InputStream is = s.getInputStream();
byte[] bys =new byte[1024];
int len =is.read(bys);
String data = new String(bys,0,len);
System.out.println("服务器:" +data);
//给出反馈
OutputStream os = s.getOutputStream();
os.write("数据收到".getBytes());
//释放资源
ss.close();
}
}
客户端
package com.itdemo_28;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
public class ClientDemo01 {
public static void main(String[] args) throws IOException {
//创建客户端的Socket对象
Socket s = new Socket("192.168.124.9",10086);
//获取输出流,写数据
OutputStream os = s.getOutputStream();
os.write("hello".getBytes());
//接收服务器反馈
InputStream is = s.getInputStream();
byte[] bys = new byte[1024];
int len =is.read(bys);
String data = new String(bys,0,len);
System.out.println("客户端:"+data);
//释放资源
// is.close();
// os.close();
//s.close后就都释放了,不需要在单独释放
s.close();
}
}
练习2
服务器端
package com.itdemo_28;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo02 {
public static void main(String[] args) throws IOException {
//创建服务器Socket
ServerSocket ss = new ServerSocket(10086);
//监听客户端的连接
Socket s = ss.accept();
//获取输入流
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
String line;
while ((line=br.readLine())!=null){
System.out.println(line);
}
//释放
ss.close();
}
}
客户端
package com.itdemo_28;
import java.io.*;
import java.net.Socket;
public class ClientDemo02 {
public static void main(String[] args) throws IOException {
//创建客户端Socket对象
Socket s = new Socket("192.168.124.9",10086);
//数据来自键盘录入,知道输入的是886,发送数据结束
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//封装输出流对象
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
String line;
while ((line=br.readLine())!=null){
if ("886".equals(line)){
break;
}
//获取输出对象
// OutputStream os = s.getOutputStream();
// os.write(line.getBytes());
//一次写一个字符串
bw.write(line);
bw.newLine();
bw.flush();
}
//释放
s.close();
}
}
练习3
服务器
package com.itdemo_28;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo03 {
public static void main(String[] args) throws IOException {
//创建Socket对象
ServerSocket ss = new ServerSocket(10086);
//监听客户端
Socket s = ss.accept();
//接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
//把数据写入文件
BufferedWriter bw = new BufferedWriter(new FileWriter("src\\s.txt"));
String line;
while ((line=br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
//释放
ss.close();
bw.close();
}
}
接收端
package com.itdemo_28;
import java.io.*;
import java.net.Socket;
public class ClientDemo02 {
public static void main(String[] args) throws IOException {
//创建客户端Socket对象
Socket s = new Socket("192.168.124.9",10086);
//数据来自键盘录入,知道输入的是886,发送数据结束
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
//封装输出流对象
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
String line;
while ((line=br.readLine())!=null){
if ("886".equals(line)){
break;
}
//获取输出对象
// OutputStream os = s.getOutputStream();
// os.write(line.getBytes());
//一次写一个字符串
bw.write(line);
bw.newLine();
bw.flush();
}
//释放
s.close();
}
}
练习4
package com.itdemo_28;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.function.BiFunction;
public class ServerDemo04 {
public static void main(String[] args) throws IOException {
//创建Socket
ServerSocket ss = new ServerSocket(10086);
//监听客户端
Socket s = ss.accept();
//接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
//把数据写入文本本间
BufferedWriter bw = new BufferedWriter(new FileWriter("src\\copy.txt"));
String line;
while ((line=br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
bw.close();
ss.close();
}
}
package com.itdemo_28;
import java.io.*;
import java.net.Socket;
public class ClientDemo04 {
public static void main(String[] args) throws IOException {
//创建Socket对象
Socket s = new Socket("192.168.124.9",10086);
// 封装文本文件
BufferedReader br = new BufferedReader(new FileReader("src\\s.txt"));
// 封装输出流写数据
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
String line;
while ((line = br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
//释放资源
br.close();
s.close();
}
}
练习5
package com.itdemo_28;
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo05 {
public static void main(String[] args) throws IOException {
//创建服务器Socket
ServerSocket ss = new ServerSocket(10086);
//监听客户端
Socket s = ss.accept();
//接收数据
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
//写入文本
BufferedWriter bw = new BufferedWriter(new FileWriter("src\\copy05.txt"));
String line;
while ((line=br.readLine())!=null){
//等待读取数据
// if ("886".equals(line)){
// break;
// }
bw.write(line);
bw.newLine();
bw.flush();
}
//给出反馈
BufferedWriter bwSer = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
bwSer.write("文件上传成功");
bwSer.newLine();
bwSer.flush();
//释放
bw.close();
ss.close();
}
}
package com.itdemo_28;
import java.io.*;
import java.net.Socket;
public class ClientDemo05 {
public static void main(String[] args) throws IOException {
//创建客户端Socket
Socket s = new Socket("192.168.124.9",10086);
//封装文本文件的数据
BufferedReader br = new BufferedReader(new FileReader("src\\s.txt"));
//封装输出流写数据
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
String line;
while ((line= br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
//自定义结束标记,虽然能解决问题,但还会有错误
// bw.write("886");
// bw.newLine();
// bw.flush();
//public void shutdownOutput()
s.shutdownOutput();
//接收反馈
BufferedReader brSer = new BufferedReader(new InputStreamReader(s.getInputStream()));
String data = brSer.readLine();//等待读取数据
System.out.println("服务器的反馈"+data);
//释放
br.close();
s.close();
}
}
练习6
package com.itdemo_29;
import java.io.*;
import java.net.Socket;
public class ClintDemo {
public static void main(String[] args) throws IOException {
//创建Socket
Socket s = new Socket("192.168.124.9",10087);
//封装文本文档
BufferedReader br = new BufferedReader(new FileReader("src\\s.txt"));
//封装输出流写数据
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
String line;
while ((line= br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
s.shutdownOutput();
//接收反馈
BufferedReader brClient = new BufferedReader(new InputStreamReader(s.getInputStream()));
String data = brClient.readLine();
System.out.println("服务器的反馈: "+data);
br.close();
s.close();
}
}
package com.itdemo_29;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerDemo {
public static void main(String[] args) throws IOException {
//服务器Socket对象
ServerSocket ss = new ServerSocket(10087);
while (true){
//监听客户端
Socket s = ss.accept();
//为每一客户端开启一个线程
new Thread(new ServerThread(s)).start();
}
}
}
package com.itdemo_29;
import java.io.*;
import java.net.Socket;
public class ServerThread implements Runnable {
private Socket s;
public ServerThread(Socket s) {
this.s = s;
}
@Override
public void run() {
//接收数据写到文件
try {
BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
// BufferedWriter bw = new BufferedWriter(new FileWriter("src\\copy111.txt"));
// 名称冲突问题
int count =0;
File file = new File("src\\copy["+count+"].txt" );
while (file.exists()){
count++;
file = new File("src\\copy["+count+"].txt");
}
BufferedWriter bw = new BufferedWriter(new FileWriter(file));
String line;
while ((line=br.readLine())!=null){
bw.write(line);
bw.newLine();
bw.flush();
}
//给出反馈
BufferedWriter bwServer = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
bwServer.write("文件上传成功");
bwServer.newLine();
bwServer.flush();
//释放
br.close();
s.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}