電子郵件發件實驗電子郵件發件實驗1電子郵件流程用戶A用戶B服務器A服務器B1、用戶A通過郵件客戶端發送郵件到服務器A2、服務器A將郵件發送到服務器B3、用戶B接受服務器B上的郵件電子郵件流程用戶A用戶B服務器A服務器B1、用戶A通過郵件客2用戶A郵件發送過程用戶A客戶端首先和服務器A建立TCP連接確認之后，用戶A和服務器A之間采用SMTP協議發送郵件內容郵件內容傳輸完畢后，發送結束用戶A郵件發送過程用戶A客戶端首先和服務器A建立TCP連接3郵件客戶端JAVA程序該程序分為4部分，分別為mailclient、envelope、message、smtpconnectionMailcilent為客戶端主程序，包括使用界面、按鍵的定義，整個的發送流程中類的創建message為發送郵件的內容部分，包含有發件人、收件人等內容envelope為用于smtp協議的信息傳遞，包含發送接收信息以及message信息smtpconnection為發件過程中和smtp連接的建立以及關閉郵件客戶端JAVA程序該程序分為4部分，分別為mailcli4發送過程中使用的指令HELO250MAILFROM250RCPTTO250DATA354QUIT221發送過程中使用的指令HELO2505MailClientimportjava.io.*;import.*;importjava.awt.*;importjava.awt.event.*;publicclassMailClientextendsFrame{ privateButtonbtSend=newButton("Send"); privateButtonbtClear=newButton("Clear"); privateButtonbtQuit=newButton("Quit"); privateLabelserverLabel=newLabel("Localmailserver:"); privateTextFieldserverField=newTextField("",40); privateLabelfromLabel=newLabel("From:"); privateTextFieldfromField=newTextField("",40); privateLabeltoLabel=newLabel("To:"); privateTextFieldtoField=newTextField("",40); privateLabelsubjectLabel=newLabel("Subject:"); privateTextFieldsubjectField=newTextField("",40);MailClientimportjava.io.*;6 privateLabelmessageLabel=newLabel("Message:"); privateTextAreamessageText=newTextArea(10,40);

/** *CreateanewMailClientwindowwithfieldsforenteringalltherelevant *information(From,To,Subject,andmessage). */ publicMailClient(){ super("JavaMailClient");

PanelserverPanel=newPanel(newBorderLayout()); PanelfromPanel=newPanel(newBorderLayout()); PaneltoPanel=newPanel(newBorderLayout()); PanelsubjectPanel=newPanel(newBorderLayout()); PanelmessagePanel=newPanel(newBorderLayout()); serverPanel.add(serverLabel,BorderLayout.WEST); serverPanel.add(serverField,BorderLayout.CENTER); fromPanel.add(fromLabel,BorderLayout.WEST); fromPanel.add(fromField,BorderLayout.CENTER); toPanel.add(toLabel,BorderLayout.WEST); privateLabelmessageLabel=7 toPanel.add(toField,BorderLayout.CENTER); subjectPanel.add(subjectLabel,BorderLayout.WEST); subjectPanel.add(subjectField,BorderLayout.CENTER); messagePanel.add(messageLabel,BorderLayout.NORTH); messagePanel.add(messageText,BorderLayout.CENTER); PanelfieldPanel=newPanel(newGridLayout(0,1)); fieldPanel.add(serverPanel); fieldPanel.add(fromPanel); fieldPanel.add(toPanel); fieldPanel.add(subjectPanel);

/**Createapanelforthebuttonsandlistenerstothebuttons.*/ PanelbuttonPanel=newPanel(newGridLayout(1,0)); btSend.addActionListener(newSendListener()); btClear.addActionListener(newClearListener()); btQuit.addActionListener(newQuitListener()); buttonPanel.add(btSend); buttonPanel.add(btClear); buttonPanel.add(btQuit); toPanel.add(toField,BorderL8

/**Add,pack,andshow*/ add(fieldPanel,BorderLayout.NORTH); add(messagePanel,BorderLayout.CENTER); add(buttonPanel,BorderLayout.SOUTH); pack(); show(); }

staticpublicvoidmain(Stringargv[]){ newMailClient(); }

/**HandlerfortheSend-button.*/ classSendListenerimplementsActionListener{ publicvoidactionPerformed(ActionEventevent){ System.out.println("Sendingmail");

/**Checkthatwehavethelocalmailserver*/ if((serverField.getText()).equals("")){ System.out.println("Neednameoflocalmailserver!");

9 return; }

/**確認發送者和接收者的郵件地址正確*/ if((fromField.getText()).equals("")){ System.out.println("Needsender!"); return; }

if((toField.getText()).equals("")){ System.out.println("Needrecipient!"); return; }

/**Createthemessage*/ MessagemailMessage=newMessage(fromField.getText(), toField.getText(), subjectField.getText(), messageText.getText());

return;10 /**Checkthatthemessageisvalid,i.e.,senderandrecipientaddressslookok.*/ if(!mailMessage.isValid()){ System.out.println("Mailisnotvalid!"); return; }

Envelopeenvelope; try { envelope=newEnvelope(mailMessage,serverField.getText()); }catch(UnknownHostExceptione){ /**Ifthereisanerror,donotgofurther*/ System.out.println("Unknownhost!"); return; }

/**Checkthatthemessagei11 try{ SMTPConnectionconnection=newSMTPConnection(envelope); connection.send(envelope); connection.close(); }catch(IOExceptionerror){ System.out.println("Sendingfailed:"+error); return; }

System.out.println("Mailsendsuccessfully!"); } } /**ClearthefieldsontheGUI.*/ classClearListenerimplementsActionListener{ publicvoidactionPerformed(ActionEvente){ System.out.println("Clearingfields"); fromField.setText(""); toField.setText(""); subjectField.setText(""); try{12 messageText.setText(""); } }

/*Quit*/ classQuitListenerimplementsActionListener{ publicvoidactionPerformed(ActionEvente){ System.exit(0); } }} messageText.setText("");13Messageimportjava.util.*;importjava.text.*;publicclassMessage{ publicStringHeaders; publicStringBody;

privateStringFrom; privateStringTo;

/**Tomakeitlooknicer*/ privatestaticfinalStringCRLF="\r\n";

/**CreatethemessageobjectbyinsertingtherequiredheadersfromRFC822(From,To,Date).*/ publicMessage(Stringfrom,Stringto,Stringsubject,Stringtext){ /**Removewhitespace*/Messageimportjava.util.*;14 From=from.trim(); To=to.trim(); Headers="From:"+From+CRLF; Headers+="To:"+To+CRLF; Headers+="Subject:"+subject.trim()+CRLF;

/**Acloseapproximationoftherequiredformat.UnfortunatelyonlyGMT.*/ SimpleDateFormatformat=newSimpleDateFormat("EEE,ddMMMyyyyHH:mm:ss'GMT'"); StringdateString=format.format(newDate()); Headers+="Date:"+dateString+CRLF; Body=text; }

/**Twofunctionstoaccessthesenderandrecipient.*/ publicStringgetFrom(){ returnFrom; }

publicStringgetTo(){ returnTo; }

From=from.trim();15 /**檢查信息的有效性，發送者和接受者的地址 *containsonlyone@-sign.*/ publicbooleanisValid(){ intfromat=From.indexOf('@'); inttoat=To.indexOf('@');

if(fromat<1||(From.length()-fromat)<=1){ System.out.println("Senderaddressisinvalid."); returnfalse; }

if(toat<1||(To.length()-toat)<=1){ System.out.println("Recipientaddressisinvalid."); returnfalse; }

if(fromat!=From.lastIndexOf('@')){ System.out.println("Senderaddressisinvalid."); returnfalse; } /**檢查信息的有效性，發送者和接受者的地址 *containsonlyone@-sign.*/ publicbooleanisValid(){ intfromat=From.indexOf('@'); inttoat=To.indexOf('@');

if(fromat<1||(From.length()-fromat)<=1){ System.out.println("Senderaddressisinvalid."); returnfalse; }

if(toat<1||(To.length()-toat)<=1){ System.out.println("Recipientaddressisinvalid."); returnfalse; }

if(fromat!=From.lastIndexOf('@')){ System.out.println("Senderaddressisinvalid."); returnfalse; }郵件客戶機分析要點課件16

if(toat!=To.lastIndexOf('@')){ System.out.println("Recipientaddressisinvalid."); returnfalse; }

returntrue; }

/**Forprintingthemessage.*/ publicStringtoString(){ Stringres;

res=Headers+CRLF; res+=Body; returnres; }}

17Envelopeimportjava.io.*;import.*;importjava.util.*;publicclassEnvelope{ publicStringSender;

/**SMTP-recipient,orcontentsofTo-header.*/ publicStringRecipient;

/**TargetMX-host*/ publicStringDestHost; publicInetAddressDestAddr;

/**Theactualmessage.*/ publicMessageMessage;

/**Createtheenvelope.*/ publicEnvelope(Messagemessage,StringlocalServer)throwsUnknownHostException{Envelopeimportjava.io.*;18 /**Getsenderandrecipient.*/ Sender=message.getFrom(); Recipient=message.getTo();

Message=escapeMessage(message);

/**TakethenameofthelocalmailserverandmapitintoanInetAddress*/ DestHost=localServer; try{ DestAddr=InetAddress.getByName(DestHost); }catch(UnknownHostExceptione){ System.out.println("UnknownHost:"+DestHost); System.out.println(e); throwe; } return; }

/**Getsenderandrecipient19

privateMessageescapeMessage(Messagemessage){ StringescapeBody=""; Stringtoken; StringTokenizerparser=newStringTokenizer(message.Body,"\n",true);

while(parser.hasMoreTokens()){ token=parser.nextToken(); if(token.startsWith(".")){ token="."+token; }

escapeBody+=token; }

message.Body=escapeBody; returnmessage; }

20 /**Forprintingtheenvelope.Onlyfordebug.*/ publicStringtoString(){ Stringres="Sender:"+Sender+"\n"; res+="Recipient:"+Recipient+"\n"; res+="MX-host:"+DestHost+",address:"+DestAddr+"\n"; res+="Message:"+"\n"; res+=Message.toString();

returnres; }} /**Forprintingtheenvelope21SMTPConnectionimport.*;importjava.io.*;importjava.util.*;publicclassSMTPConnection{ privateSocketconnection;

/**Streamsforreadingandwritingthesocket*/ privateBufferedReaderfromServer; privateDataOutputStreamtoServer;

privatestaticfinalintSMTP_PORT=25; privatestaticfinalStringCRLF="\r\n";

/**Areweconnected?Usedinclose()todeterminewhattodo.*/ privatebooleanisConnected=false;

SMTPConnectionimport.22 /**CreateanSMTPConnectionobject.Createthesocketandtheassociatedstreams.Initialize *SMTPconnection. */ publicSMTPConnection(Envelopeenvelope)throwsIOException{ connection=newSocket(envelope.DestAddr,SMTP_PORT); fromServer=newBufferedReader(newInputStreamReader(connection.getInputStream())); toServer=newDataOutputStream(connection.getOutputStream());

/**Readalinefromserverandcheckthatthereplycodeis220.Ifnot,throwanIOException.*/ Stringreply=fromServer.readLine(); if(reply.startsWith("220")){

}else{ thrownewIOException("Serverreply"+reply); }

/**CreateanSMTPConnection23 /**SMTPhandshake.Weneedthenameofthelocalmachine. *SendtheappropriateSMTPhandshakecommand.*/ Stringlocalhost=envelope.DestHost; try{ sendCommand("HELO"+localhost,250); }catch(IOExceptionerror){ System.out.println(error); System.exit(1); }catch(Exceptione){ System.out.println(e); System.exit(1); }

isConnected=true; }

/**Sendthemessage.WritethecorrectSMTP-commandsinthecorrectorder.Nocheckingforerrors, *justthrowthemtothecaller. */ publicvoidsend(Envelopeenvelope)throwsIOException{ /**SMTPhandshake.Weneed24 /**Sendallthenecessarycommandstosendamessage.CallsendCommand()todothedirty *work.Do_not_catchtheexceptionthrownfromsendCommand(). */ sendCommand("MAILFROM:"+envelope.Sender+CRLF,250); sendCommand("RCPTTO:"+envelope.Recipient+CRLF,250); sendCommand("DATA"+CRLF+envelope.Message.Headers+envelope.Message.Body+CRLF+"."+CRLF,354); }

/**Closetheconnection.First,terminateonSMTPlevel,thenclosethesocket.*/ publicvoidclose(){ isConnected=false; try{ /** sendCommand("QUIT",221);*/ sendCommand("QUIT",250); connection.close(); } /**Sendallthenecessaryc25catch(IOExceptione){ System.out.println("Unabletocloseconnection:"+e); isConnected=true; } }

/**SendanSMTPcommandtotheserver.Checkthatthereplycodeiswhatisissupposedtobe *accordingtoRFC821. */ privatevoidsendCommand(Stringcommand,intrc)throwsIOException{ Stringreply;

toServer.writeBytes(command); toServer.writeBytes(CRLF); System.out.println("Me:"+command+'\n'); reply=fromServer.readLine(); System.out.println("Server:"+reply+'\n'); if(!reply.startsWith(String.valueOf(rc))){ thrownewIOException("Serverreply:"+reply); }

catch(IOExceptione){26 /** if(rc!=parseReply(reply)){ thrownewIOException("Serverreply"+reply); }*/ /** if((command.equalsIgnoreCase("HELO")&&rc!=250)