《JAVA程序设计（第二版）》教学课件

//程序名：TelnetApp.Java import java.applet.*; import java.awt.*; import java.io.*; import java.net.*; import java.util.*; public class TelnetApp extends Applet implements Runnable { //声明成员变量 Thread client; TextArea log; TextField hostname; TextField userid; TextField password; Label hname; Label uid; Label psd; Button connect; Button bye; int wantTime; boolean logged; Socket socket = null; PrintStream os; DataInputStream is; public TelnetApp(){} public void init(){ resize(400, 300); setLayout(new BorderLayout()); Panel p1 = new Panel(); log = new TextArea(10, 80); log.setEditable(false); p1.add(log); add("North", p1); Panel p2 = new Panel(); p2.add(hname = new Label("Hostname:")); p2.add(hostname = new TextField(20)); p2.add(uid = new Label("Userid:")); p2.add(userid = new TextField(10)); p2.add(psd = new Label("Password:")); p2.add(password = new TextField(10)); password.setEchoCharacter('*'); add("Center", p2); Panel p3 = new Panel(); p3.add(connect = new Button("Connect")); p3.add(bye = new Button("Bye")); bye.disable(); add("South", p3); logged = false; } public void run(){ String fromServer = null; byte b[] = new byte[3]; b[0] = (byte)'n'; while(true){ if((fromServer = getData())!=null) log.appendText(fromServer+"\n"); if(wantTime <0){ bye(); break; } if(logged){ delay(60*1000); log.setText(""); wantTime-=1; sendData(b, 1); } } } // 建立主机连接 private boolean connectHost(String hostName){ try{ socket = new Socket(hostName, 23); os = new PrintStream(socket.getOutputStream()); is = new DataInputStream(socket.getInputStream()); }catch(UnknownHostException e){ log.setText("Trying to connect to unknown host:" + e); return false; }catch(Exception e){ log.setText("Exception: "+e); return false; } return true; } // 接收信息 String getData(){ String fromServer; int len; byte b[] = new byte[1000]; try{ fromServer = ""; len = is.read(b); fromServer += new String(b, 0); }catch(Exception e){ log.setText("Exception: "+e); return null; } return fromServer; } // 发送信息 boolean sendData(byte b[], int len){ try{ os.write(b, 0, len); os.flush(); }catch(Exception e){ log.setText("Exception: "+e); return false; } return true; } //关闭连接 void closeSocket(){ try{ os.close(); is.close(); socket.close(); socket = null; }catch(Exception e){ log.setText("Exception: "+e); } } void toByte(byte[] b, String s){ int i; for(i=0;i<s.length();i++) b[i]=(byte)s.charAt(i); b[i] = 13; b[i+1] = 10; } void negotiate(){ byte b[] = new byte[20]; b[0]=-1;b[1]=-5;b[2]=24; sendData(b, 3); delay(400); b[0]=-1;b[1]=-6;b[2]=24; b[3]=0;b[4]=(byte)'D';b[5]=(byte)'E'; b[6]=(byte)'C';b[7]=(byte)'-';b[8]=(byte)'V'; b[9]=(byte)'T';b[10]=(byte)'1';b[11]=(byte)'0'; b[12]=(byte)'0';b[13]=-1;b[14]=-16; sendData(b, 15); delay(400); b[0]=-1;b[1]=-3;b[2]=1; b[3]=-1;b[4]=-3;b[5]=3; b[6]=-1;b[7]=-5;b[8]=31; b[9]=-1;b[10]=-4;b[11]=-56; b[12]=-1;b[13]=-5;b[14]=1; sendData(b, 15); delay(400); // 在bbs上注册 toByte(b, "bbs"); sendData(b, 5); delay(400); } void login(String userid, String password){ byte b[] = new byte[20]; toByte(b, userid); sendData(b, userid.length()+2); delay(400); toByte(b, password); sendData(b, password.length()+2); delay(400); } boolean enter(){ if(connectHost(hostname.getText().trim())){ log.setText("connected\n"); negotiate(); delay(400); login(userid.getText().trim(), password.getText().trim()); delay(400); return true; }else return false; } void toMainmenu(){ byte b[] = new byte[20]; for(int i=0;i<6;i++){ toByte(b, ""); sendData(b, 2); } for(int i=0;i<1;i++){ b[0] = (byte)'q'; sendData(b, 1); delay(200); } } void bye(){ byte b[] = new byte[20]; for(int i=0;i<10;i++){ b[0] = (byte)'q'; sendData(b, 1); delay(300); } b[0]=(byte)'g'; sendData(b, 1); delay(300); for(int i=0;i<6;i++){ toByte(b, ""); sendData(b, 2); delay(300); } client.stop(); client=null; closeSocket(); connect.enable(); bye.disable(); } void delay(int millisecond){ try{ Thread.sleep(millisecond); }catch(InterruptedException e){ } } public boolean action(Event e, Object arg){ switch(e.id){ case Event.ACTION_EVENT: if(e.target == connect){ wantTime = 20; connect.disable(); bye.enable(); client = new Thread(this); client.start(); if(enter()) toMainmenu(); logged = true; }else if(e.target == bye) bye(); } return true; } public void destroy(){} public void paint(Graphics g){} public void start(){} public void stop(){} }