清华大学：JAVA教学课件：12-7

//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(){}
}