网络编程基础类
InetAddress类
- java.net.InetAddress类用来封装计算机的IP地址和DNS(没有端口信息),它包括一个主机名和一个ip地址,是java对IP地址的高层表示。大多数其他网络类都要用到这个类，包括Sorket、ServerSocker、URL、DatagramSorket、DatagramPacket等
- 常用静态方法
-
- getLocalHost()得到本机的InetAddress对象,其中封装了IP地址和主机名
- getByName(String host)传入目标主机的名字或IP地址得到对应的InetAddress对象,其中封装了IP地址和主机名(底层会自动连接DNS服务器进行域名解析)
-
- getHostAddress() 获取IP地址
- getHostName() 获取主机名/域名
public class Test01 {public static void main(String[] args) throws UnknownHostException {//获取本机InetAddress对象(包含ip地址和封装对象)InetAddress ia = InetAddress.getLocalHost();//获取本机ip地址String ip = ia.getHostAddress();//获取本机主机名String hostName = ia.getHostName();System.out.println(ip + " -> " + hostName); //10.6.43.36 -> DESKTOP-D4BI28V//通过getByName(String host) 获取指定地址的InetAddress对象InetAddress baidu = InetAddress.getByName("baidu.com");System.out.println(baidu.getHostAddress()); //39.156.66.10System.out.println(baidu.getHostName()); //baidu.com}
}
URL类
- URL由4部分组长城：协议、存放资源的主机域名、端口号、资源文件名。未指定端口号则使用协议默认的端口
- 标准格式 <协议>://<域名/IP>:<端口号>/<路径>
-
- <协议>://<域名/IP>是必须的
- <端口号>/<路径>有时可省略
- 为了方便程序员编程，JDK中提供了URL类，该类的全名是java.net.URL，该类封装了大量复杂的涉及从远程站点获取信息的细节，可以使用它的各种方法来对URL对象进行分割、合并等处理
-
-
- Url url = new URL(String url);
public class Test01 {public static void main(String[] args) throws UnknownHostException, MalformedURLException {URL url = new URL("https://www.baidu.com/s?wd=%E5%BC%A0%E4%B8%89&rsv_spt=1&rsv_iqid=0x901ef519004b0a02&issp=1&f=8&rsv_bp=1&rsv_idx=2&ie=utf-8&rqlang=&tn=baiduhome_pg&ch=&rsv_enter=1&rsv_btype=i&rsv_dl=ib&inputT=2117");//获取协议String protocol = url.getProtocol();System.out.println("协议" + protocol);//获取域名String host = url.getHost();System.out.println("域名" + host);//获取默认端口int defaultPort = url.getDefaultPort();System.out.println("默认端口" + defaultPort);//获取端口int port = url.getPort();System.out.println("端口" + port);//获取路径String path = url.getPath();System.out.println("路径" + path);//获取资源String file = url.getFile();System.out.println("资源" + file);//获取数据String query = url.getQuery();System.out.println("数据" + query);//获取锚点String ref = url.getRef();System.out.println("锚点" + ref);}
}
-
- 使用URL类的openStream()方法可以打开到此URL的连接并返回一个用于从该链接读入的InputStream,实现最简单的网络爬虫
public class Test01 {public static void main(String[] args){//获取URL对象指向tianqi.qq.comURL url = null;InputStream is = null;BufferedReader br = null;try {url = new URL("https://tianqi.qq.com/");//获取简单输入流is = url.openStream();//通过转换流获取包装流br = new BufferedReader(new InputStreamReader(is));String str = null;while ((str = br.readLine()) != null) {System.out.println(str);}} catch (MalformedURLException e) {throw new RuntimeException(e);} catch (IOException e) {throw new RuntimeException(e);}finally {//关闭流if (is != null) {try {is.close();} catch (IOException e) {throw new RuntimeException(e);}}if (br != null) {try {br.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}
TCP协议用到的类
Socket套接字类
- 我们开发的网络应用程序位于应用层，TCP和UDP属于传输层协议，在应用层如何使用传输层的服务呢?在应用层和传输层之间，则是使用套接Socket来进行分离。
- 套接字就像是传输层为应用层开的一个小口，应用程序通过这个小口向远程发送数据，或者接收远程发来的数据。而这个小口以内，也就是数据进入这个口之后，或者数据从这个口出来之前，是不知道也不需要知道的，也不会关心它如何传输，这属于网络其它层次工作。
- Socket实际是传输层供给应用层的编程接口。Socket就是应用层与传输层之间的桥梁。使用Socket编程可以开发客户机和服务器应用程序，可以在本地网络上进行通信，也可通过Internet在全球范围内通信。
- TCP协议和UDP协议是传输层的两种协议。Socket是传输层供给应用层的编程接口，所以Socket编程就分为TCP编程和UDP编程两类。
构造方法
- public Socket(InetAddress a,int p)
- public Socket(String ip,int p)
实例方法
ServerSocket类
- ServerSocket类用于实现服务器套接字（Server服务端）。服务器套接字等待请求通过网络传入。它基于该请求执行某些操作，然后可能向请求者返回结果
构造方法
-
- public ServerSocket(int port)
实例方法
UDP协议用到的的类
DatagramPacket类
- DatagramSocket类作为基于UDP协议的Socket,使用DatagramSocket类可以用于接收和发送数据,同时创建接收端时还需指定端口号
- 构造方法
-
- receive(DatagramPacket p)
DatagramPacket类
- DatagramPacket类负责把发送的数据打包(打包的数据为byte类型的数组)，并且创建发送端时需指定接收端的IP地址和端口
- 构造方法
-
- DatagramPacket(byte bufp[],int offset,int length)
-
- DatagramPacket(byte bufp[],int offset,int length,InetAddress address,int port)
-
- public synchronized byte[] getDate()
-
- public synchronized int getLength()
基于TCP协议的程序
服务端与客户端的单项通讯（client -> server）
public class Server {public static void main(String[] args) {//新建ServerSocket对象ServerSocket server = null;Socket client = null;BufferedReader br = null;try {int port = 8888;server = new ServerSocket(port);System.out.println("服务器启动成功，端口号为" + port);//服务端开始侦听并接收请求，获取到来自服务端的Socket对象client = server.accept();System.out.println("已经与" + client.getInetAddress() + ':' + client.getPort() + "建立连接");//获取服务端输入流br = new BufferedReader(new InputStreamReader(client.getInputStream()));System.out.println(br);String str = null;while ((str = br.readLine()) != null) {System.out.println("客户端:");System.out.println(str);}} catch (IOException e) {throw new RuntimeException(e);} finally {if (br != null) {try {br.close();} catch (IOException e) {throw new RuntimeException(e);}}if (server != null) {try {server.close();} catch (IOException e) {throw new RuntimeException(e);}}if (client != null) {try {client.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}
public class Client {public static void main(String[] args) {//创建客户端Socket对象Socket client = null;BufferedWriter bw = null;try {InetAddress localHost = InetAddress.getLocalHost();client = new Socket(localHost,8888);//client = new Socket("127.0.0.1",8888); 传ip地址也可以//转换为增强字符流bw = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));Scanner sc = new Scanner(System.in);//发送内容while (true) {bw.write(sc.next() + '\n');bw.flush();Thread.sleep(1000L);}} catch (IOException e) {throw new RuntimeException(e);} catch (InterruptedException e) {throw new RuntimeException(e);} finally {if (client != null) {try {client.close();} catch (IOException e) {throw new RuntimeException(e);}}if (bw != null) {try {bw.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}
- 细节：readLine()是读一行，因此必须有换行符才能连续读取
服务端客户端双向通信(客户端--->服务端-->客户端)
public class Server {public static void main(String[] args) {ServerSocket serverSocket = null;Socket clientSocket = null;BufferedInputStream bis = null;BufferedOutputStream bos = null;BufferedWriter bw = null;try {//新建服务器对象serverSocket = new ServerSocket(8888);//开始侦听8888端口接受连接并返回Socket套接字对象clientSocket = serverSocket.accept();System.out.println("已经连接到" + clientSocket.getInetAddress() + ':' + clientSocket.getPort());//获取缓冲字节输入/出流,缓冲字符输出流bis = new BufferedInputStream(clientSocket.getInputStream());bos = new BufferedOutputStream(new FileOutputStream("C:\\temp\\temp2.png"));bw = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));byte[] bytes = new byte[1024];int i = 0;int len = 0;while ((len = bis.read(bytes)) != -1) {bos.write(bytes,0,len);//刷新缓冲流bos.flush();}bw.write("传输成功");//传输完成,返回信息bw.flush();} catch (IOException e) {throw new RuntimeException(e);} finally {if (serverSocket == null) {try {serverSocket.close();} catch (IOException e) {throw new RuntimeException(e);}}if (clientSocket != null) {try {clientSocket.close();} catch (IOException e) {throw new RuntimeException(e);}}if (bis != null) {try {bis.close();} catch (IOException e) {throw new RuntimeException(e);}}if (bos != null) {try {bos.close();} catch (IOException e) {throw new RuntimeException(e);}}if (bw != null) {try {bw.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}
public class Client {public static void main(String[] args) {Socket clientSocket = null;BufferedOutputStream bos = null;BufferedInputStream bis = null;BufferedReader br = null;try {//创建客户端SocketclientSocket = new Socket(InetAddress.getLocalHost(),8888);//获取缓冲输出/入字节流,缓冲字符输入流bis = new BufferedInputStream(new FileInputStream(new File("C:\\temp\\temp1.png")));bos = new BufferedOutputStream(clientSocket.getOutputStream());br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));byte[] bytes = new byte[1024];//发送图片int len = 0;while ((len = bis.read(bytes)) != -1) {//发送图片bos.write(bytes,0,len);//刷新缓冲流bos.flush();len = bis.read(bytes);}//输出结束，Server端停止接收数据clientSocket.shutdownOutput();String str = null;//等待接收消息while ((str = br.readLine()) != null) {System.out.println(str);}} catch (UnknownHostException e) {throw new RuntimeException(e);} catch (IOException e) {throw new RuntimeException(e);} finally {if (clientSocket != null) {try {clientSocket.close();} catch (IOException e) {throw new RuntimeException(e);}}if (bos != null) {try {bos.close();} catch (IOException e) {throw new RuntimeException(e);}}if (bis != null) {try {bis.close();} catch (IOException e) {throw new RuntimeException(e);}}if (br != null) {try {br.close();} catch (IOException e) {throw new RuntimeException(e);}}}}
}
-
- 服务端的输入流是从客户端得到的，客户端while循环结束后，服务器仍在监听客户端，等待客户端发送消息，因此客户端不会继续往下执行,必须调用shutdownOutput()方法，声明输出流已停止输出，客户端才会继续往下执行
基于UDP协议的程序
public class Recive {public static void main(String[] args) {DatagramSocket recive = null;DatagramPacket datagramPacket = null;try {//新建接收端DatagramSocket对象recive = new DatagramSocket(8888);//创建数据包byte[] bytes = new byte[1024];datagramPacket = new DatagramPacket(bytes,0,bytes.length);//接收数据报recive.receive(datagramPacket);//转实际长度System.out.println(new String(bytes,0,datagramPacket.getLength()));} catch (SocketException e) {throw new RuntimeException(e);} catch (IOException e) {throw new RuntimeException(e);} finally {if (recive != null) {recive.close();}}}
}
public class Send {public static void main(String[] args) {DatagramSocket send = null;DatagramPacket datagramPacket = null;try {//新建发送端DatagramSocket对象send = new DatagramSocket();//准备要发送的数据byte[] bytes = "Hello,world".getBytes();//创建发送包datagramPacket = new DatagramPacket(bytes,0,bytes.length,InetAddress.getByName("127.0.0.1"),8888);//发送数据send.send(datagramPacket);} catch (SocketException e) {throw new RuntimeException(e);} catch (UnknownHostException e) {throw new RuntimeException(e);} catch (IOException e) {throw new RuntimeException(e);} finally {if (send != null) {send.close();}}}
}
