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什么是网络编程？
网络编程建立在公共协议TCP/IP或者IOS协议的基础上，通过套接字的服务机制实现不同主机的联系。
网络编程的通讯要素
IP地址
网络中设备的识别，本地回环地址为127.0.0.1，主机名：localHost
端口号
用于标识不同进程的逻辑地址
传输协议
常用的协议是：UDP和TCP
获取主机网络地址对象
InetAddress inetaddress1 = InetAddress.getByName("www.baidu.com")或者
InetAddress inetaddress2 = InetAddress.getByName("192.168.1.1"）
获取主机名
String hostname = inetaddress1.getHostName();
获取主机地址
String hostaddress = inetaddress1.getHostAddress();
套接字Socket
Socket是一种服务接口，它提供的服务能够实现数据包的传递
UDP协议特点
面向无连接，不可靠协议
数据报大小限制在64k内
传输速度快，容易丢包
TCP协议特点
面向连接，可靠协议，三次握手，建立连接
在连接中可进行大数据的传输
传输安全，速度慢
UDP传输
UDP发送数据报步骤：
1：建立DatagramSocket对象服务
DatagramSocket datagramsocket = new DatagramSocket();
2：建立数据报DatagramPacket对象
byte[] a = "hei ma cheng xu yuan".getBytes();
DatagramPacket datagrampacket = new DatagramPacket（a,a.length,InetAddress.getByName("192.168.1.1",10000);
3：发送数据包
datagramsocket.send(datagrampacket);
4:关闭Socket
datagramsocket.close();
UDP接收数据步骤
1：建立DatagramSocket对象服务
DatagramSocket datagramsocket = new DatagramSocket(10000);
2：建立数据报DatagramPacket对象
byte[] a = new byte[1024];
DatagramPacket datagrampacket = new DatagramPacket（a,a.length);
3：通过Socket服务的receive()方法把接收到的数据封装到已经准备好的数据包中
datagramsocket.receive();
4.通过接收到的数据包提供的方法，获取数据包中各种数据
返回主机对象
InetAddress inetaddress = a.getAddress();
获取主机名
String hostname = inetaddress1.getHostName();
获取主机地址
String hostaddress = inetaddress1.getHostAddress();
返回数据内容
byte[] data = a.getData();
String b = new String(data,0,data.length());
返回端口号
int port = a.getPort();
5,关闭Socket流
datagramsocket.close();
Tcp传输
Tcp客户端
1：建立套接字服务
Socket socket = new Socket(InetAddress.getByName("192.168.1.1",10000);
2:获取流
OutputStream output = socket.getOutputStream();
3:通过输入流写入数据
byte[] data = "ke hu duan qing qiu lian jie".getBytes();
int len = output.write(data);
4:关闭流
socket.close();
Tcp服务端
1：建立套接字服务,并监听端口
ServerSocket serversocket = new ServerSocket(10000);
2:获取连接过来的客户端对象
Socket socket = serversockt.accept();
3:获取客户端连接过来的流,并读取相关数据
InputStream input = socket .getInputStream();
byte[] data = new byte[1024];
int len = data.read(data);
4.关闭流
serversocket.close();
URL
什么是URL
其实就是表示网页地址的字符串
建立URL对象
URL url1 = new URL("https://www.baidu.com/");
URL url2 = new URL("https://192.168.1.254:8080/myweb/demo.html");
获取URL对象方法
url2.getFile();获取文件名
url2.getHost();获取主机名
url2.getPort();获取端口号
url2.getPath();获取路径
url2.getProtocol();获取协议
url2.getQuery();获取查询部
连接到服务端
URLconnection urlconnection = url2.openConnection();
1 练习
2 /*
3 * 编写一个聊天程序，有收数据的部分，有发数据的部分
4 */
5 package bolgtest;
6 import java.io.*;
7 import java.net.*;
8 public class UdpTest {
9 public static void main(String[] args)throws Exception {
10 DatagramSocket datagramsocket1 = new DatagramSocket();
11 DatagramSocket datagramsocket2 = new DatagramSocket(10000);
12
13 UdpSend send = new UdpSend(datagramsocket1);
14 UdpReceive receive = new UdpReceive(datagramsocket2);
15 Thread thread1 = new Thread(send);
16 Thread thread2 = new Thread(receive);
17 thread1.start();
18 thread2.start();
19
20 }
21 }
22 class UdpSend implements Runnable{
23 private DatagramSocket datagramsocket = null;
24 UdpSend(DatagramSocket socket){
25 this.datagramsocket = socket;
26 }
27 public void run(){
28 BufferedReader buffer = null;
29 try{
30 buffer = new BufferedReader(new InputStreamReader(System.in));
31 String str = null;
32 while( (str = buffer.readLine())!=null)
33 {
34 if("886".equals(str))
35 break;
36 byte[] data = str.getBytes();
37 DatagramPacket datagrampacket = new DatagramPacket(data,data.length,InetAddress.getByName("192.168.1.255"),10000);
38 datagramsocket.send(datagrampacket);
39 }
40 }catch(Exception e){
41 throw new RuntimeException("出错啦");
42 }
43 finally{
44 try{
45 buffer.close();
46 }catch(Exception e){
47 throw new RuntimeException("出错啦");
48 }
49 }
50 }
51 }
52
53 class UdpReceive implements Runnable{
54 private DatagramSocket datagramsocket = null;
55 UdpReceive(DatagramSocket socket){
56 this.datagramsocket = socket;
57 }
58 public void run(){
59 BufferedReader buffer = null;
60 while(true){
61 try{
62 byte[] data = new byte[1024];
63 DatagramPacket datagrampacket = new DatagramPacket(data,data.length);
64 datagramsocket.receive(datagrampacket);
65 String str = new String(datagrampacket.getData(),0,datagrampacket.getData().length);
66 String str2 = datagrampacket.getAddress().getHostAddress();
67 System.out.print(str2+":"+str);
68 }catch(Exception e){
69 throw new RuntimeException("出错啦");
70 }
71 }
72
73
74
75 }
76 }
1 练习
2 /*
3 * 把客户端的一个文件传到服务端去，并且在服务端中存储起来
4 */
5 package bolgtest;
6 import java.io.*;
7 import java.net.*;
8 public class ClientTest {
9 public static void main(String[] args) {
10 try{
11 Socket socket = new Socket("192.168.1.101",10000);
12 BufferedWriter buffwriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
13 BufferedReader clientreader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
14 BufferedReader buffread = new BufferedReader(new FileReader("F:\\BaiduYunDownload\\client.txt"));
15 String str =null;
16 while((str = buffread.readLine())!=null){
17 buffwriter.write(str);
18 buffwriter.newLine();
19 buffwriter.flush();
20 }
21 socket.shutdownOutput();
22 String str1 = null;
23 while((str1 = clientreader.readLine())!=null){
24 System.out.println(str1);
25 }
26 }catch(Exception e){
27 System.out.println(e.getMessage());
28 }
29
30
31
32 }
33 }
34
35 package bolgtest;
36 import java.io.*;
37 import java.net.ServerSocket;
38 import java.net.Socket;
39 public class ServerTest {
40 public static void main(String[] args)throws Exception {
41 ServerSocket server = new ServerSocket(10000);
42 Socket socket = server.accept();
43 BufferedReader buffreader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
44 BufferedWriter buffwriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
45 PrintWriter printwriter = new PrintWriter(new FileWriter("F:\\BaiduYunDownload\\copy.txt"),true);
46 String str = null;
47 while((str = buffreader.readLine())!=null){
48 printwriter.println(str);
49 }
50 buffwriter.write("上传成功");
51 buffwriter.newLine();
52 buffwriter.flush();
53
54 }
55 }
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