java的网络编程

一：基础的网络编程

1.InetAddress

 1 import java.net.InetAddress;
 2 public class Test128 {
 3     public static void main(String[] args) throws Exception {
 4         //inetMethod();
 5         inetMethod2();
 6     }
 7     public static void inetMethod()throws Exception{
 8         //local的问题
 9         InetAddress i=InetAddress.getLocalHost();
10         String address=i.getHostAddress();
11         String name=i.getHostName();
12         System.out.println("address="+address);
13         System.out.println("name="+name);
14     }
15     public static void inetMethod2()throws Exception{
16         //根据域名来处理        
17         InetAddress ia=InetAddress.getByName("www.baidu.com");
18         String address=ia.getHostAddress();
19         String name=ia.getHostName();
20         System.out.println("address="+address);
21         System.out.println("name="+name);
22     }
23 
24 }

二：UDP

1.接收端

 1 import java.net.DatagramPacket;
 2 import java.net.DatagramSocket;
 3 
 4 public class Test130 {
 5 
 6     public static void main(String[] args) throws Exception {
 7         reviceShow();
 8 
 9     }
10     public static void reviceShow()throws Exception{
11         DatagramSocket ds=new DatagramSocket(10004);
12         byte[] buf=new byte[1024];
13         DatagramPacket dp=new DatagramPacket(buf,buf.length);
14         ds.receive(dp);
15         String ip=dp.getAddress().getHostAddress();
16         String data=new String(dp.getData(),0,dp.getLength());
17         int port=dp.getPort();
18         System.out.println("ip="+ip);
19         System.out.println("data="+data);
20         System.out.println("port="+port);
21     }
22 
23 }

2.发送端

 1 import java.net.DatagramPacket;
 2 import java.net.DatagramSocket;
 3 import java.net.InetAddress;
 4 
 5 /**
 6  * 发送端
 7  * @author Administrator
 8  *
 9  */
10 public class Test129 {
11     public static void main(String[] args) throws Exception {
12         sendShow();        
13     }
14     public static void sendShow()throws Exception{
15         DatagramSocket ds=new DatagramSocket();
16         byte[] buf="info send".getBytes();
17         DatagramPacket dp=new DatagramPacket(buf,buf.length,
18                 InetAddress.getByName("10.66.130.139"),10004);
19         ds.send(dp);
20         ds.close();
21     }
22 }

三：TCP

1.通信，交换图片（但是一次）

先是服务端：

 1 import java.io.FileOutputStream;
 2 import java.io.IOException;
 3 import java.io.InputStream;
 4 import java.io.OutputStream;
 5 import java.net.ServerSocket;
 6 import java.net.Socket;
 7 
 8 /**
 9  * 服务端
10  * @author Administrator
11  *
12  */
13 public class Test123 {
14 
15     public static void main(String[] args) throws Exception {
16         ServerSocket ss=new ServerSocket(10009);
17         Socket s=ss.accept();
18         InputStream in=s.getInputStream();
19         FileOutputStream fos=new FileOutputStream("shsj.jpg");
20         byte[] buf=new byte[1024];
21         int len=0;
22         while((len=in.read(buf))!=-1){
23             fos.write(buf, 0, len);
24         }
25         OutputStream out=s.getOutputStream();
26         out.write("成功".getBytes());
27         fos.close();
28         s.close();
29         ss.close();
30     }
31 
32 }

再是客户端：

 1 import java.io.FileInputStream;
 2 import java.io.IOException;
 3 import java.io.InputStream;
 4 import java.io.OutputStream;
 5 import java.net.Socket;
 6 import java.net.UnknownHostException;
 7 
 8 /**
 9  * 发送端
10  * @author Administrator
11  *
12  */
13 public class Test122 {
14     public static void main(String[] args) throws Exception {
15         Socket s=new Socket("10.66.113.25",10009);
16         FileInputStream fis=new FileInputStream("u.jpg");
17         OutputStream out=s.getOutputStream();
18         byte[] buf=new byte[1024];
19         int len=0;
20         while((len=fis.read(buf))!=-1){
21             out.write(buf, 0, len);
22         }
23         //important
24         s.shutdownOutput();
25         InputStream ins=s.getInputStream();
26         byte[] bufin=new byte[1024];
27         int num=ins.read(bufin);
28         System.out.println(new String(bufin,0,num));
29         fis.close();
30         ins.close();
31         s.close();
32     }
33 
34 }

2.多线程服务端

先写客户端

注意添加一些限制条件，同时，这里是添加的参数是文件路径

 1 import java.io.File;
 2 import java.io.FileInputStream;
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 import java.io.OutputStream;
 6 import java.net.Socket;
 7 import java.net.UnknownHostException;
 8 
 9 public class Test124 {
10 
11     public static void main(String[] args) throws Exception {
12         if(args.length!=1){
13             System.out.println("choose a pic");
14             return;
15         }
16         File file=new File(args[0]);
17         if(!(file.exists()&&file.isFile())){
18             System.out.println("file have problem");
19             return;
20         }
21         if(!file.getName().endsWith(".jpg")){
22             System.out.println("file type is error");
23             return;
24         }
25         if(file.length()>1024*1024*5){
26             System.out.println("file > 5M");
27             return;
28         }
29         Socket s=new Socket("10.66.113.25",10019);
30         FileInputStream fis=new FileInputStream(file);
31         OutputStream out=s.getOutputStream();
32         byte[] buf=new byte[1024];
33         int len=0;
34         while((len=fis.read(buf))!=-1){
35             out.write(buf, 0, len);
36         }
37         s.shutdownOutput();
38         InputStream in=s.getInputStream();
39         byte[] bufin=new byte[1024];
40         int num=in.read(bufin);
41         String str=new String(bufin,0,num);
42         fis.close();
43         s.close();        
44     }
45 }

再写服务端

 1 import java.io.File;
 2 import java.io.FileOutputStream;
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 import java.io.OutputStream;
 6 import java.net.ServerSocket;
 7 import java.net.Socket;
 8 
 9 /**
10  * 服务端
11  * @author Administrator
12  *
13  */
14 public class Test125 {
15 
16     public static void main(String[] args) throws Exception {
17         ServerSocket ss=new ServerSocket(10019);
18         while(true){
19             Socket s=ss.accept();
20             new Thread(new ServerThread(s)).start();
21         }
22     }
23 }
24 /**
25  * 需要一个多线程的类
26  * 下面类是用在服务端的类
27  */
28 class ServerThread implements Runnable{
29     private Socket s;
30     public ServerThread(Socket s){
31         this.s=s;
32     }
33     public void run(){
34         int count=1;
35         String ip=s.getInetAddress().getHostAddress();
36         try{
37             System.out.println(ip+"connect");
38             InputStream ins=s.getInputStream();
39             File dir=new File("d:\pic");
40             File file=new File(dir,ip+"("+count+").jpg");
41             while(file.exists()){
42                 file=new File(dir,ip+"("+(count++)+").jpg");
43             }
44             FileOutputStream fos=new FileOutputStream(file);
45             byte[] buf=new byte[1024];
46             int len=0;
47             while((len=ins.read(buf))!=-1){
48                 fos.write(buf, 0, len);
49             }
50             OutputStream out=s.getOutputStream();
51             out.write("success".getBytes());
52             fos.close();
53             s.close();
54             
55         }catch(Exception e){
56             new RuntimeException();
57         }
58     }
59 }

3.客户端并发登录

服务端

 1 import java.io.BufferedReader;
 2 import java.io.FileReader;
 3 import java.io.InputStreamReader;
 4 import java.io.PrintWriter;
 5 import java.net.ServerSocket;
 6 import java.net.Socket;
 7 
 8 public class Test127 {
 9 
10     public static void main(String[] args) throws Exception{
11         ServerSocket ss=new ServerSocket(10089);
12         while(true){
13             Socket s=ss.accept();
14             new Thread(new LoginThread(s)).start();
15         }
16     }
17 }
18 class LoginThread implements Runnable{
19     private Socket s;
20     LoginThread(Socket s){
21         this.s=s;
22     }
23     public void run(){
24         String ip=s.getInetAddress().getHostAddress();
25         System.out.println("ip="+ip+" connect");
26         try{
27             for(int i=0;i<3;i++){
28                 BufferedReader bufin=new BufferedReader(new InputStreamReader(
29                         s.getInputStream()));
30                 String str=bufin.readLine();
31                 if(str==null)
32                     break;
33                 BufferedReader buf=new BufferedReader(new FileReader("user.txt"));
34                 PrintWriter out=new PrintWriter(s.getOutputStream(),true);
35                 String line=null;
36                 boolean flag=false;
37                 while((line=buf.readLine())!=null){
38                     if(line.equals(str)){
39                         flag=true;
40                         break;
41                     }
42                 }
43                 if(flag){
44                     System.out.println(str+"已登录");
45                     out.println(str+"欢迎登录");
46                     break;
47                 }else{
48                     System.out.println(str+"尝试登录");
49                     out.println(str+"用户不存在");
50                 }
51             }
52         }catch(Exception e){
53             throw new RuntimeException(ip+"failed");
54         }
55     }
56 }

客户端

 1 import java.io.BufferedReader;
 2 import java.io.IOException;
 3 import java.io.InputStreamReader;
 4 import java.io.PrintWriter;
 5 import java.net.Socket;
 6 import java.net.UnknownHostException;
 7 
 8 /**
 9  * client
10  * @author Administrator
11  *
12  */
13 public class Test126 {
14 
15     public static void main(String[] args) throws Exception {
16         Socket s=new Socket("10.66.113.25",10089);
17         //键盘录入
18         BufferedReader bufr=new BufferedReader(new InputStreamReader(System.in));
19         //输出到服务端
20         PrintWriter out=new PrintWriter(s.getOutputStream(),true);
21         //读取返回内容
22         BufferedReader bufin=new BufferedReader(
23                 new InputStreamReader(s.getInputStream()));
24         //次数
25         for(int x=0;x<3;x++){
26             String line=bufr.readLine();
27             if(line==null)
28                 break;
29             out.println(line);
30             String info=bufin.readLine();
31             System.out.println("info="+info);
32             if("info".contains("欢迎"))
33                 break;
34         }
35         bufr.close();
36         s.close();
37 
38     }
39 
40 
41 }
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原文地址：https://www.cnblogs.com/juncaoit/p/6922826.html