以下例开始本文的内容:
例1,需求:上传图片。
客户端:
- 服务端点。
- 读取客户端已有的图片数据。
- 通过socket输出流将数据发给服务端。
- 读取服务端反馈信息。
- 关闭。
class PicClient { public static void main(String[] args) throws IOException { /* * 一系列判断 */ if(args.length != 1) { System.out.println("请选择一个jpg格式的图片"); return; } File file = new File(args[0]); if(!(file.exists() && file.isFile())) { System.out.println("该文件有问题,要么不存在,要么不是文件"); return; } if(!file.getName().endsWith(".jpg")) { System.out.println("图片格式错误,请重新选择"); return; } if(file.length() > 1024*1024*10) { System.out.println("文件过大,没安好心"); return; } Socket s = new Socket("10.48.62.209", 10007); FileInputStream fis = new FileInputStream(file); OutputStream out = s.getOutputStream(); byte[] buf = new byte[1024]; int len = 0; while((len = fis.read(buf)) != -1) { out.write(buf, 0, len); } //告诉服务端数据已写完 s.shutdownOutput(); InputStream in = s.getInputStream(); byte[] bufIn = new byte[1024]; int num = in.read(bufIn); System.out.println(new String(bufIn, 0, num)); fis.close(); s.close(); } }
服务端:
这个服务端有个局限性,当A客户端连接上以后,被服务端获取到,服务端执行具体流程。这时B客户端连接,只有等待,因为服务端还没有处理完A客户端的请求,还没有循环回来执行下一次accpet()方法,所以暂时获取不到B客户端对象。
那么为了可以让多个客户端同时并发访问服务端,服务端最好就是将每个客户端封装到一个单独的线程中,这样就可以同时处理多个客户端请求。
那么如何定义线程呢?
只要明确了每一个客户端在服务端执行的代码即可。将该代码存入run()方法中。
class PicThread implements Runnable { private Socket s; PicThread(Socket s) { this.s = s; } @Override public void run() { int count = 1; String ip = s.getInetAddress().getHostAddress(); try { System.out.println(ip+"......connected."); InputStream in = s.getInputStream(); File file = new File(ip+"("+(count)+")"+".jpg");//10.48.62.209(1).jpg while(file.exists()) { file = new File(ip+"("+(count++)+")"+".jpg"); } FileOutputStream fos = new FileOutputStream(file); byte[] buf = new byte[1024]; int len = 0; while((len = in.read(buf)) != -1) { fos.write(buf, 0, len); } OutputStream out = s.getOutputStream(); out.write("上传成功".getBytes()); fos.close(); s.close(); } catch (IOException e) { throw new RuntimeException(ip+"上传失败"); } } }
class PicServer { public static void main(String[] args) throws IOException { ServerSocket ss = new ServerSocket(10007); while(true) { Socket s = ss.accept(); new Thread(new PicThread(s)).start(); } //ss.close(); } }
我觉得多线程是比较难理解的,所以图示以上原理:
例2,客户端通过键盘录入用户名。服务端对这个用户名进行校验。如果该用户存在,在服务端显示XXX,已登录。并在客户端显示XXX,欢迎光临。如果该用户不存在,在服务端显示XXX,尝试登录。并在客户端显示XXX,该用户不存在。最多就登录3次。
以下为代码,导包就不导了。
客户端:
class LoginClient { public static void main(String[] args) throws IOException { Socket s = new Socket("10.48.62.209", 10008); BufferedReader bufr = new BufferedReader(new InputStreamReader(System.in)); PrintWriter out = new PrintWriter(s.getOutputStream(), true); BufferedReader bufIn = new BufferedReader(new InputStreamReader(s.getInputStream())); for(int x = 0; x < 3; x++) { /* * 在键盘敲Ctrl+C键,即代表结束录入 * read()方法返回-1,readLine()方法返回null */ String line = bufr.readLine();//Ctrl+C,那么就是-1,readLine()返回null if(line == null) break; out.println(line); String info = bufIn.readLine(); System.out.println("info:"+info); if(info.contains("欢迎")) break; } bufr.close(); s.close();//socket流中加了一个-1,相当于给流中加入一个结束标记,即-1 } }
服务端:
class UserThread implements Runnable { private Socket s; UserThread(Socket s) { this.s = s; } @Override public void run() { String ip = s.getInetAddress().getHostAddress(); System.out.println(ip+"........connected."); try { for(int x = 0; x < 3; x++) { BufferedReader bufIn = new BufferedReader( new InputStreamReader(s.getInputStream())); /* * 客户端那边敲入Ctrl+C键键时, * read()返回-1,readLine()返回null。 * 所以name得加一个判断 */ String name = bufIn.readLine(); if(name == null) break; /* * 校验 */ BufferedReader bufr = new BufferedReader(new FileReader("user.txt")); PrintWriter out = new PrintWriter(s.getOutputStream(), true); String line = null; boolean flag = false;//定义标记 while((line = bufr.readLine()) != null) { if(line.equals(name)) { flag = true; break; } } if(flag) { System.out.println(name+",已登录"); out.println(name+",欢迎光临"); break; } else { System.out.println(name+"尝试登录"); out.println(name+",用户名不存在"); } } s.close(); } catch (IOException e) { throw new RuntimeException(ip+"校验失败"); } } }
class LoginServer { public static void main(String[] args) throws IOException { ServerSocket ss = new ServerSocket(10008); while(true) { Socket s = ss.accept(); new Thread(new UserThread(s)).start(); } } }
演示客户端和服务端
1、
客户端:浏览器、telnet(远程登录命令——在DOS命令行下连接网络上任意一台主机)
形如:
telnet 10.48.62.209 11000
示例代码:
public class ServerDemo { public static void main(String[] args) throws IOException { ServerSocket ss = new ServerSocket(11000); Socket s = ss.accept(); System.out.println(s.getInetAddress().getHostAddress()); InputStream in = s.getInputStream(); byte[] buf = new byte[1024]; int len = in.read(buf); System.out.println(new String(buf, 0, len)); PrintWriter out = new PrintWriter(s.getOutputStream(), true); out.println("<font color='red' size='7'>Client, hello!!!</font>"); s.close(); ss.close(); } }
控制台输出类似诸如以下信息(头信息):
GET / HTTP/1.1 Host: 127.0.0.1:11000 Connection: keep-alive Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36 Accept-Encoding: gzip, deflate, sdch Accept-Language: zh-CN,zh;q=0.8
分析如下:
http(http协议)://127.0.0.1(主机名):11000(端口号)/myWeb(资源路径)/demo.html(资源) Host: 127.0.0.1:11000 Connection: keep-alive Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*(代表可接受任意类型的东东);q=0.8 Upgrade-Insecure-Requests: 1 User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36 Accept-Encoding: gzip(告诉服务器的压缩方式), deflate, sdch Accept-Language: zh-CN,zh;q=0.8
2、
客户端:浏览器。
服务器:Tomcat服务器。
3、
客户端:自定义。
服务器:Tomcat服务器。
示例代码:
public class MyIE { public static void main(String[] args) throws IOException { Socket s = new Socket("127.0.0.1", 8888); PrintWriter out = new PrintWriter(s.getOutputStream(), true); out.println("GET /myWeb/demo.html HTTP/1.1"); out.println("Accept: */*"); out.println("Accept-Language: zh-CN,zh;q=0.8"); out.println("Host: 127.0.0.1:11000"); out.println("Connection: closed"); /* * 注意:HTML头信息和主体信息之间一定要有一个空行 * 为了保证安全,所以索性加了两行 */ out.println(); out.println(); BufferedReader bufr = new BufferedReader( new InputStreamReader(s.getInputStream())); String line = null; while((line = bufr.readLine()) != null) { System.out.println(line); } s.close(); } }
控制台会打印类似信息:
自定义图形界面浏览器:
代码如下(导包就不导了):
public class MyIEByGUI { private Frame f; private TextField tf; private Button but; private TextArea ta; private Dialog d; private Label lab; private Button okBut; MyIEByGUI() { init(); } public void init() { f = new Frame("my window"); f.setBounds(300, 100, 600, 500); f.setLayout(new FlowLayout()); tf = new TextField(60); but = new Button("转到"); ta = new TextArea(25, 70); /* * 对话框,也是一个窗体,最好不要加到Frame里面去 */ d = new Dialog(f, "提示信息-self", true);//true:对话框不处理掉,后面的窗体是无法操作的!! d.setBounds(400, 200, 240, 150); d.setLayout(new FlowLayout()); lab = new Label(); okBut = new Button("确定"); d.add(lab); d.add(okBut); f.add(tf); f.add(but); f.add(ta); myEvent(); f.setVisible(true); } private void myEvent() { //点击对话框中的确定按钮,对话框也不显示出来 okBut.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { d.setVisible(false); } }); /* * 关闭对话框,对话框不显示 */ d.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { d.setVisible(false); } }); tf.addKeyListener(new KeyAdapter() { @Override public void keyPressed(KeyEvent e) { if(e.getKeyCode() == KeyEvent.VK_ENTER) { try { showDir(); } catch (IOException e1) { e1.printStackTrace(); } } } }); /* * 按钮是事件源 */ but.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { try { showDir(); } catch (IOException e1) { e1.printStackTrace(); } } }); f.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { System.exit(0); } }); } private void showDir() throws IOException { ta.setText(""); /* * http://127.0.0.1:8888/myWeb/demo.html * 以下代码只不过是拆解url字符串路径而已 */ String url = tf.getText(); int index1 = url.indexOf("//")+2; int index2 = url.indexOf("/", index1); String str = url.substring(index1, index2); String[] arr = str.split(":"); String host = arr[0]; int port = Integer.parseInt(arr[1]); String path = url.substring(index2); //ta.setText(str+"....."+path); Socket s = new Socket(host, port); PrintWriter out = new PrintWriter(s.getOutputStream(), true); out.println("GET "+path+" HTTP/1.1"); out.println("Accept: */*"); out.println("Accept-Language: zh-CN,zh;q=0.8"); out.println("Host: 127.0.0.1:11000"); out.println("Connection: closed"); out.println(); out.println(); BufferedReader bufr = new BufferedReader( new InputStreamReader(s.getInputStream())); String line = null; while((line = bufr.readLine()) != null) { ta.append(line+" "); } s.close(); } public static void main(String[] args) { new MyIEByGUI(); } }
运行效果图:
URL
示例代码:
/* String getFile() 获取此 URL 的文件名。 String getHost() 获取此 URL 的主机名(如果适用)。 String getPath() 获取此 URL 的路径部分。 int getPort() 获取此 URL 的端口号。 String getProtocol() 获取此 URL 的协议名称。 String getQuery() 获取此 URL 的查询部分。 */ import java.net.MalformedURLException; import java.net.URL; public class URLDemo { public static void main(String[] args) throws MalformedURLException { URL url = new URL("http://127.0.0.1/myWeb/demo.html?name=haha&age=30"); System.out.println("getProtocol():"+url.getProtocol());//http System.out.println("getHost():"+url.getHost());//127.0.0.1 System.out.println("getPort():"+url.getPort()); System.out.println("getPath():"+url.getPath());//---/myWeb/demo.html System.out.println("getFile():"+url.getFile());//---/myWeb/demo.html?name=haha&age=30 System.out.println("getQuery():"+url.getQuery());//name=haha&age=30 /* 不写端口时,给一个默认的端口号80 int port = getPort(); if(port == -1) port = 80; */ } }
URLConnection(似乎封装了Socket)
示例代码:
import java.io.IOException; import java.io.InputStream; import java.net.URL; import java.net.URLConnection; public class URLConnectionDemo { public static void main(String[] args) throws IOException { URL url = new URL("http://127.0.0.1:8888/myWeb/demo.html"); URLConnection conn = url.openConnection(); System.out.println(conn); InputStream in = conn.getInputStream(); byte[] buf = new byte[1024]; int len = in.read(buf); System.out.println(new String(buf, 0, len)); } }
所以自定义图形界面浏览器代码优化之后为:
public class MyIEByGUI2 { private Frame f; private TextField tf; private Button but; private TextArea ta; private Dialog d; private Label lab; private Button okBut; MyIEByGUI2() { init(); } public void init() { f = new Frame("my window"); f.setBounds(300, 100, 600, 500); f.setLayout(new FlowLayout()); tf = new TextField(60); but = new Button("转到"); ta = new TextArea(25, 70); /* * 对话框,也是一个窗体,最好不要加到Frame里面去 */ d = new Dialog(f, "提示信息-self", true);//true:对话框不处理掉,后面的窗体是无法操作的!! d.setBounds(400, 200, 240, 150); d.setLayout(new FlowLayout()); lab = new Label(); okBut = new Button("确定"); d.add(lab); d.add(okBut); f.add(tf); f.add(but); f.add(ta); myEvent(); f.setVisible(true); } private void myEvent() { //点击对话框中的确定按钮,对话框也不显示出来 okBut.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { d.setVisible(false); } }); /* * 关闭对话框,对话框不显示 */ d.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { d.setVisible(false); } }); tf.addKeyListener(new KeyAdapter() { @Override public void keyPressed(KeyEvent e) { if(e.getKeyCode() == KeyEvent.VK_ENTER) { try { showDir(); } catch (IOException e1) { e1.printStackTrace(); } } } }); /* * 按钮是事件源 */ but.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { try { showDir(); } catch (IOException e1) { e1.printStackTrace(); } } }); f.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { System.exit(0); } }); } private void showDir() throws IOException { ta.setText(""); /* * http://127.0.0.1:8888/myWeb/demo.html */ String urlPath = tf.getText(); URL url = new URL(urlPath); URLConnection conn = url.openConnection(); //System.out.println(conn); InputStream in = conn.getInputStream(); byte[] buf = new byte[1024]; int len = in.read(buf); ta.setText(new String(buf, 0, len)); } public static void main(String[] args) { new MyIEByGUI2(); } }
图示原理:
域名解析