... 用JAVA实现SMTP 服务器

				
				import java.io.InputStream;
				import java.io.IOException;
				
				public class Request
				{  
				  public static final int  HELO=0;
				  public static final int  MAIL=1;
				  public static final int  RCPT=2;
				  public static final int  DATA=3;
				  public static final int  NOOP=4;
				  public static final int  RESET=5;
				  public static final int  QUIT=6;
				  public static final int UNKNOWENCMD=7;
				  
				  public static final int  ERROR=-1;
				  
				  public InputStream  input;
				  
				  public String request;
				  public String cmd;
				 
				  public int requestType;
				  public String string;
				  public String domain;
				  public String user;
				  public String revrsePath;
				  public String forwordPath;
				 
				  
				  
				  public int getRequestType(){return requestType;}
				  public String getUser(){ return user;}
				  public String getRevrsePath(){return revrsePath;}
				  public String getForwordPath(){return forwordPath;}
				  public String getRequestCmd(){return cmd;}
				  public String getRequest(){ return request;}
				  public String Domain(){return domain;}
				  public String getString(){ return string;}
				  
				  public void clear()
				   {
				  	user="";
				  	revrsePath="";
				  	forwordPath="";
				  	domain="";
				  	string="";
				  	
				   }//清空用户信息
				  
				  
				  public Request()
				  
				   {
				  	requestType=ERROR;
				  
				   }
				  
				   
				   public Request(InputStream input)
				  
				   {
				  	this.input=input;
				  
				   }//构造函数，初始化input对象
				  
				  
				   
				  public String getMsg()
				   {
				  	StringBuffer requestBuf=new StringBuffer(1024);//申请字符空间
				  	int i;
				  	byte[] buffer=new byte[1024];//字节数组
				  	
				     try 
				     {
				      i=input.read(buffer);//从输入流中读用户信息并且保存在字节数组里
				     } 
				     
				  catch(IOException www)
				     {
					www.printStackTrace();//出现IO错误，打印错误信息
					i=-1;//将读取量设置为0
				     }
				   for(int j=0;j				     {
				   	  requestBuf.append((char) buffer[j]);//将字节数组转化为字符串
				     }   
				      System.out.println(requestBuf.toString());
				      request=requestBuf.toString().trim();
				      jiexi();
				      return request;
				    }
				    
				 public void jiexi()
				   { 
				   
				   int index=request.indexOf(' ');
				   if(index				   else cmd=request.substring(0,index).toUpperCase();
				   //提取出用户名令
				   
				   if(cmd.equals("HELO"))
				     {
				   	  requestType=HELO;
				   	  domain=request.substring(index+1,request.length());
				   	  return;
				   	
				     }
				     //判断是否为HELO命令
				   
				   
				   if(cmd.equals("MAIL"))
				    {
				   	
				   	 requestType=MAIL;
				   	 int x=request.indexOf('				   	 int y=request.indexOf('>');
				   	 revrsePath=request.substring(x+1,y); 
				   	 return;
				    }
				    //判断是否为mail命令，提取出revrsePath变量
				   
				   if(cmd.equals("RCPT"))
				    {
				    	requestType=RCPT;
				    	int x1=request.indexOf('				   	    int y1=request.indexOf('>');
				   	    forwordPath=request.substring(x1+1,y1);
				   	    int z=forwordPath.indexOf('@');
				   	    if(z>0)
				   	    {
				   	    	
				   	    	user=forwordPath.substring(0,z);
				   	    	
				   	    }
				   	    
				   	      else user="";
				   	    
				   	    return;
				     }
				       //判断是否为RCPT命令，提取出forwordPath，user变量
				    
				    if(cmd.equals("DATA"))
				     {
				     	requestType=DATA;
				     	return;
				     }
				     //判断是否为DATA名林
				     
				     if(cmd.equals("RESET"))
				     {
				     	requestType=RESET;
				     	return;
				     }
				 	//判断是否为reset命令
				 	 if(cmd.equals("NOOP"))
				     {
				     	requestType=NOOP;
				     	return;
				     }
				     //判断是否为noop命令
				     if(cmd.equals("QUIT"))
				     {
				     	requestType=QUIT;
				     	
				     	return;
				     }
				     //判断是否为quit命令
				     requestType=UNKNOWENCMD;//如果不是七命令就为未知命令
				    
				     
				 }
				}