什么是网络编程？
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是指将地理位置不同的具有独立功能的多台计算机及其外部设备，通过通信线路连接起来，在网络操作系统，网络管理软件及网络通信协议的管理和协调下，实现资源共享和信息传递的计算机系统。
网络编程的目的：
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传播交流信息。
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数据交换。
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通信。
如何达到此效果？
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需要准确的定位网络上的一台主机，例如：192.168.25.31：port（端口）
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找到主机传输数据。
网络通信要素：
如何实现网络通讯？
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IP
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端口号
192.168.1.1：8080
CMD命令查询网址IP
ping www.baidu.com
端口号（0~65535）
不同的进程有不同的端口号，端口号不可冲突！用来区分软件
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公有端口：0~1023
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HTTP：80
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HTTPS：443
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FTP：21
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Telent: 23
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…
-
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注册端口：1024~49151
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Tomcat：8080
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MySQL：3306
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Oracle：1521
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…
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动态、私有端口：49152~65535
网络编程
InetAddress
InetAddress localIpAddress = InetAddress.getLocalHost();
System.out.println(localIpAddress); // = DESKTOP-DOPS1I8/192.168.43.50
// 通过主机ip地址或域名，ip获取ip地址对象
InetAddress byName = InetAddress.getByName("127.0.0.1");
System.out.println(byName); // = /127.0.0.1
// 通过主机名获取多个ip地址对象
InetAddress[] allByName = InetAddress.getAllByName("www.baidu.com");
Arrays.asList(allByName).stream().forEach(System.out::println); // www.baidu.com/182.61.200.6 www.baidu.com/182.61.200.7
InetAddress loopbackAddress = InetAddress.getLoopbackAddress();// 获取回环ip地址对象
System.out.println(loopbackAddress); // = localhost/127.0.0.1
/**
* 常用方法
**/
byte[] address = localIpAddress.getAddress();
System.out.println(address); // = [B@682a0b20
String canonicalHostName = localIpAddress.getCanonicalHostName(); // 规范主机名
System.out.println(canonicalHostName); // = DESKTOP-DOPS1I8
String hostAddress = localIpAddress.getHostAddress(); // 主机ip地址
System.out.println(hostAddress); // = 192.168.137.1
String hostName = localIpAddress.getHostName();// 主机名
System.out.println(hostName); // = DESKTOP-DOPS1I8
boolean reachable = localIpAddress.isReachable(3000);// 3s内是否可到达
System.out.println(reachable); // = true
InetSocketAddress
InetSocketAddress inetSocketAddress = new InetSocketAddress("xx", 80);
InetAddress address = inetSocketAddress.getAddress(); // ip地址对象
System.out.println(address); // null
String hostName = inetSocketAddress.getHostName(); // 主机名
System.out.println(hostName); // xx
String hostString = inetSocketAddress.getHostString(); // 主机字符串
System.out.println(hostString); // xx
int port = inetSocketAddress.getPort();// 端口
System.out.println(port); // 80
boolean unresolved = inetSocketAddress.isUnresolved(); // 主机名是否不能被解析为ip地址对象
System.out.println(unresolved); // true （不能解析）
通信协议
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TCP：用户传输协议
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连接，稳定
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客户端、服务器
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传输完成，释放连接，效率低
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UDP：用户数据报协议
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不连接，不稳定
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客户端服务器：没有明确的界面
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不管有没有准备好都可以发给你
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导弹
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TCP
客户端：
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连接服务器Socket。
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发送消息。
public static void main(String[] args) throws IOException { Socket socket = null; OutputStream os = null; try { //1.要知道服务器的地址，端口号 InetAddress server = InetAddress.getByName("127.0.0.1"); int port = 9999; socket = new Socket(server,port); //传入IP地址和端口号 os = socket.getOutputStream(); os.write("你好，我是发送者".getBytes()); } catch (IOException e) { e.printStackTrace(); }finally { socket.close(); os.close(); } }
服务器：
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建立服务端口SeverSocket。
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等待用户连接accept。
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接收用户消息。
public static void main(String[] args) throws IOException { ServerSocket serverSocket = null; Socket socket = null; InputStream is = null; ByteArrayOutputStream baos = null; try { //地址：localhost 9999 serverSocket = new ServerSocket(9999); System.out.println("server running..."); socket = serverSocket.accept(); is = socket.getInputStream();//读取客户端的消息 baos = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len; while ((len = is.read(buffer))!=-1){ baos.write(buffer,0,len); } System.out.println(baos.toString()); } catch (IOException e) { e.printStackTrace(); }finally { baos.close(); is.close(); socket.close(); serverSocket.close(); } }
文件上传
服务器
public static void main(String[] args) throws IOException {
ServerSocket serverSocket = new ServerSocket(9000); //创建服务
Socket socket = serverSocket.accept();//阻塞式接听，会一定等待客户连接
InputStream is = socket.getInputStream(); //获取输入流
FileOutputStream fos = new FileOutputStream(new File("receive.png"));
byte[] buffer = new byte[1024];
int len;
while ((len = is.read(buffer))!=-1){
fos.write(buffer,0,len);
}
OutputStream os = socket.getOutputStream(); //通知客户端接收完毕了
os.write("接收完毕".getBytes());
fos.close();
is.close();
socket.close();
serverSocket.close();
}
客户端
public static void main(String[] args) throws IOException {
Socket socket = new Socket(InetAddress.getByName("127.0.0.1"), 9000);//创建一个Socket连接
OutputStream os = socket.getOutputStream(); //创建一个输出流
FileInputStream fis = new FileInputStream(new File("基础语法/src/T1.png")); //读取文件
byte[] buffer = new byte[1024];
int len;
while ((len = fis.read(buffer))!=-1){
os.write(buffer,0,len);
}
socket.shutdownOutput(); //传输完毕
InputStream inputStream = socket.getInputStream(); //服务器接收完毕才能断开连接
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] bytes = new byte[2014];
int len2;
while ((len2=inputStream.read(bytes))!=-1){
baos.write(bytes,0,len2);
}
System.out.println(baos.toString());
fis.close();
os.close();
socket.close();
}
UDP
发短信：不用连接，需要知道对方地址
发送消息
public static void main(String[] args) throws Exception {
//建立一个socket
DatagramSocket socket = new DatagramSocket();
//键个包
String msg = "你好啊,服务器";
//发送给谁
InetAddress localhost = InetAddress.getByName("localhost");
int port = 9090;
DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);
//发送包
socket.send(packet);
socket.close();
}
接收段
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);
//阻塞接收
socket.receive(packet);
System.out.println(packet.getAddress().getHostAddress()); // = 127.0.0.1
System.out.println(new String(packet.getData(),0,packet.getLength())); // = 你好啊,服务器
socket.close();
}
循环发送
public static void main(String[] args) throws Exception {
DatagramSocket socket = new DatagramSocket(8888);
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //准备数据控制台读取System.in
while (true){
String data = reader.readLine();
byte[] datas = data.getBytes();
DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress("localhost",6667));
socket.send(packet);
if (data.equals("bye")){
break;
}
}
socket.close()
}
接收
public static void main(String[] args) throws Exception{
DatagramSocket socket = new DatagramSocket(6667);
while (true){
byte[] container = new byte[1024];
DatagramPacket packet = new DatagramPacket(container,0,container.length);
socket.receive(packet);
byte[] data = packet.getData();
String receiveData = new String(data,0,data.length);
System.out.println(receiveData);
if (receiveData.equals("bye")){
break;
}
}
socket.close();
}
双方同时接收
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) {
e.printStackTrace();
}
}
@Override
public void run() {
while (true) {
try {
//准备接收数据
byte[] bytes = new byte[1024];
DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length);//阻塞式接收包裹
socket.receive(packet);
//断开连接
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) {
e.printStackTrace();
}
}
socket.close();
}
}
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);
//准备数据 从控制台读取
reader = new BufferedReader(new InputStreamReader(System.in));
} catch (SocketException e) {
e.printStackTrace();
}
}
@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 (IOException e) {
e.printStackTrace();
}
}
socket.close();
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
首先开始老师线程
public class TalkTeacher {
public static void main(String[] args) {
//开启两个线程
new Thread(new TalkSend(6661,"localhost",8881)).start();
new Thread(new TalkReceive(9992,"学生")).start();
}
}
然后开启学生线程
public class TalkStudent {
public static void main(String[] args) {
//开启两个线程
new Thread(new TalkSend(7777,"localhost",9992)).start();
new Thread(new TalkReceive(8881,"老师")).start();
}
}
URL
统一资源定位符：定位资源的，定位互联网上的某一资源
DNS 域名解析 www.baidu.com
协议：// ip 地址 : 端口 / 项目名/资源
import java.net.URL;
public static void main(String[] args) throws Exception {
URL url = new URL("http://localhost:8080/hello/index.jsp?username=zr&password=88");
System.out.println(url.getProtocol()); //协议 = http
System.out.println(url.getHost()); //主机IP = localhost
System.out.println(url.getPort()); //端口 = 8080
System.out.println(url.getPath()); //文件 = /hello/index.jsp
System.out.println(url.getFile()); //全路径 = /hello/index.jsp?username=zr&password=88
System.out.println(url.getQuery()); //参数 = username=zr&password=88
}
下载网络资源
public static void main(String[] args) throws IOException {
URL url = new URL("http://localhost:8080/guanxin/Theguan.png"); //资源地址
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream is = urlConnection.getInputStream(); //连接得到这个资源
FileOutputStream fos = new FileOutputStream("基础语法/src/guan.png");
byte[] buffer = new byte[1024];
int len;
while ((len=is.read(buffer))!=-1){
fos.write(buffer,0, len); //写出数据
}
//断开连接
fos.close();
is.close();
urlConnection.disconnect();
}
破茧
URL url = new URL("https://ws.stream.qqmusic.qq.com/C400003kSb8X2Ie1Ue.m4a?guid=435264108&vkey=D5D47FCEDC99D48B2C242AB949F2E59EA91478AC83CD892AEDD5F26D0D59E6A09A203B60628F4F69EC16EBB470CC3B6D22137FE893103726&uin=1064936282&fromtag=66");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
InputStream is = urlConnection.getInputStream();
FileOutputStream fos = new FileOutputStream("基础语法/src/pojian.m4a");
byte[] buffer = new byte[1024];
int len;
while ((len=is.read(buffer))!=-1){
fos.write(buffer,0, len);//写出数据
}
fos.close();
is.close();
urlConnection.disconnect();
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