实验七 应用层网络编程（一）(2)

2. POP3编程（参考电子讲义“网络编程参考资料-应用层.pdf”及教材“第

2章 Socket编程”）

阅读 “网络编程参考资料-应用层.pdf”中 8.3.2部分，实现“POP3客户实现”的源代码（Pop3ClientDemo.java），并在机器上编译运行通过。（注：可输入城院POP3邮件服务器pop3.email.zucc.edu.cn或其他邮件服务器作为POP3服务器） 【程序源代码】

Pop3ClientDemo.java import java.io.*; import java.net.*; import java.util.*;

public class Pop3ClientDemo { protected int port = 110;

protected String hostname = \ protected String username = \ protected String password = \

protected Socket socket; protected BufferedReader br; protected PrintWriter pw;

// Constructs a new instance of the POP3 client public Pop3ClientDemo() throws Exception { try {

// Get user input getInput();

// Get mail messages displayEmails(); } catch(Exception e) {

System.err.println (\ e.printStackTrace();

System.out.println(e.getMessage()); } }

// Returns TRUE if POP response indicates success, FALSE if failure protected boolean responseIsOk() throws Exception { String line = br.readLine(); System.out.println(\

// 和 SMTP 不同的地方，POP3 的回覆不再是一個 number 而是 // +OK 來代表要求成功。失敗則以 -ERR 來代表。 return line.toUpperCase().startsWith(\ }

// Reads a line from the POP server, and displays it to screen protected String readLine(boolean debug) throws Exception { String line = br.readLine();

// Append a < character to indicate this is a server protocol response if (debug)

System.out.println(\ else

System.out.println(line); return line; }

// Writes a line to the POP server, and displays it to the screen protected void writeMsg(String msg) throws Exception {

pw.println(msg); pw.flush();

System.out.println(\ }

// Close all writers, streams and sockets

protected void closeConnection() throws Exception { pw.flush(); pw.close(); br.close();

socket.close(); }

// Send the QUIT command, and close connection protected void sendQuit() throws Exception { System.out.println(\ writeMsg(\ readLine(true);

System.out.println(\ closeConnection(); }

// Display emails in a message

protected void displayEmails() throws Exception {

BufferedReader userinput = new BufferedReader( new InputStreamReader (System.in) );

System.out.println(\ \

System.out.println(\ \

// Open a connection to POP3 server System.out.println(\

socket = new Socket(this.hostname, this.port);

br = new BufferedReader(new InputStreamReader(socket.getInputStream())); pw = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));

// If response from server is not okay

if(! responseIsOk()) { socket.close();

throw new Exception(\ }

// Login by sending USER and PASS commands System.out.println(\ writeMsg(\ if(!responseIsOk()) { sendQuit();

throw new Exception(\ }

System.out.println(\ writeMsg(\ if(!responseIsOk()) { sendQuit();

throw new Exception(\ }

// Get mail count from server .... System.out.println(\ writeMsg(\

// ... and parse for number of messages String line = readLine(true);

StringTokenizer tokens = new StringTokenizer(line,\

// +OK

tokens.nextToken();

// number of messages

int messages = Integer.parseInt(tokens.nextToken());

// size of all messages

int maxsize = Integer.parseInt(tokens.nextToken());

if (messages == 0) {

System.out.println (\ sendQuit(); return; }

System.out.println (\ System.out.println(\ userinput.readLine();

for(int i = 1; i <= messages ; i++) {

System.out.println(\ writeMsg(\

System.out.println(\ line = readLine(false);

while(line != null && !line.equals(\ line = readLine(false); }

System.out.println(\

System.out.println(\ \ String response = userinput.readLine(); if (response.toUpperCase().startsWith(\ break; }

sendQuit(); }

public static void main(String[] args) throws Exception { Pop3ClientDemo client = new Pop3ClientDemo(); }

// Read user input

protected void getInput() throws Exception { String data=null; BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

System.out.print(\ data = br.readLine();

if(data == null || data.equals(\ else hostname=data;

System.out.print(\ data = br.readLine();

if(!(data == null || data.equals(\ username=data;

System.out.print(\ data = br.readLine();

if(!(data == null || data.equals(\

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