pop3流程

一：客户端与POP3邮件服务器建立通信链接，并建立Socket的输入/输出数据流：

cs=new Socket(InetAddress.getByName(host),Integer.parseInt(port));

inData=new BufferedReader(new InputStreamReader(cs.getInputStream()));

outData=new BufferedWriter(new OutputStreamReader(cs.getOutputStream()));

二：处理用户身份验证：

msg=“USER“+user;

if(!POP3Request(msg))

return false;

if(!POP3Response())

return false;

msg=“PASS“+pass;

if(!POP3Request(msg))

return false;

if(!POP3Response())

return false;

三：处理邮件接收事务：

msg=“RETR“+mailNo;

if(!POP3Request(msg))

return false;

response=inData.readLine();

if(!response.startsWith("+OK")){

   JOptionPane.showMessageDialog((Component)null,response,“POP3 Error“,JOptionPane.ERROR_MESSAGE);

return false;

}

else{

  while(true){

    response=inData.readLine();

   if(response.trim().equals(““)&& !endofHeader){

     endofHeader=true;

     continue;

    }

    if(!endofHeader){

     if(response.startsWith(“Date:“)){

     date=response.substring(response.index(“:“)+2);

      header=header+response+linesep;

     }

if(response.startsWith(“From:“)){

     from=response.substring(response.index(“:“)+2);

      header=header+response+linesep;

     }

if(response.startsWith(“Reply-To:“)){

          header=header+response+linesep;

     }

if(response.startsWith(“Subject:“)){

     subject=response.substring(response.index(“:“)+2);

      header=header+response+linesep;

     }

if(response.startsWith(“To:“)){

     if(to.equals(““))

        to=response.substring(response.index(“:“)+2);

     else

        to=to+“,“+response.substring(response.index(“:“)+2);

      header=header+response+linesep;

     }

if(response.startsWith(“Receipients:“)){

     if(to.equals(““))

        to=response.substring(response.index(“:“)+2);

     else

        to=to+“,“+response.substring(response.index(“:“)+2);

      header=header+response+linesep;

     }

if(response.startsWith(“MIME-Version:“)){

          header=header+response+linesep;

     }

if(response.startsWith(“Content-Transfer-Encoding:“)){

          header=header+response+linesep;

     }

if(response.startsWith(“Content-Type:“)){

          header=header+response+linesep;

     }

if(response.startsWith(“Content-Description:“)){

          header=header+response+linesep;

     }

if(response.startsWith(“Message-ID:“)){

          header=header+response+linesep;

     }

    }

else{

if(response.startsWith(“.“)){

content=content+response+linesep;

break;

}

content=content+response+linesep;

}

  }

}

四：发送QUIT指令至服务器，关闭输入/输出数据流及Socket。

try{

if((outData!=null) && (inData!=null) && (cs!=null)){

msg=“QUIT“;

flag=POP3Request(msg);

flag=POP3Response();

 

}

if(outData!=null) outData.close();

if(inData!=null) inData.close();

if(cs!=null)cs.close();

}catch(IOException ex){}

System.exit(0);