JAVA POP3 Server 信件內文中斷符號問題修正

接續著上一篇 JAVA POP3 Server 實作 後，
這一篇主要是修正一個很奇怪的問題。


在使用Thunderbird測試一段時間後發現一個很奇怪的問題
只要跑一段時間就會出現 "RETR 命令不成功，取回郵件時發生錯誤"

在Outlook下測試卻不會，但會有很奇怪的空白信件，
空白信件的大小甚至可以到200M，這太不尋常了

反復測試 bug track後，
發現應該是信件內有 RETR cammond 的中斷符號造成。

至於兩個 Client 對於此問題的出現不一樣的結果，
我只能說，各家對於問題處裡的方式不同。

Thunderbird遇到問題就停止收信。
Outlook則是繼續收，但有問題的信跟後續的幾封信，都會變成空白信件。

之後有試著自己處理output時遇到中斷點問題，
但後來參考了 Apache James 的 POP3Handler Source Code ，
覺得寫的比較好，就拿來用了

看程式吧~
=============================================================
為了使用 FilterOutputStream 所以要加上 BufferedOutputStream

修改前
out = new PrintWriter(mySocket.getOutputStream(), AUTOFLUSH);

修改後
outs = new BufferedOutputStream(mySocket.getOutputStream(), 1024);
out = new PrintWriter(outs, AUTOFLUSH);

=============================================================
printMail 修改，使用 Apache James 的 ExtraDotOutputStream 來處理內文斷點

修改前
private void printMail(Integer index) {
String str = "";
GridFSDBFile gfsdbf = glist.get(index - 1);
InputStream inputS = null;
BufferedReader reader = null;
try {
inputS = gfsdbf.getInputStream();
reader = new BufferedReader(new InputStreamReader(inputS));

while ((str = reader.readLine()) != null) {
out.println(str);
}

} catch (Exception e) {
log.error(ExceptionUtils.getStackTrace(e));
} finally {
try {
if (inputS != null)
inputS.close();
if (reader != null)
reader.close();
} catch (Throwable ignore) {
}
}
}

修改後
private void printMail(Integer index) {
GridFSDBFile gfsdbf = glist.get(index - 1);
InputStream inputS = null;
try {
inputS = gfsdbf.getInputStream();

ExtraDotOutputStream edouts =
                    new ExtraDotOutputStream(outs);

int numRead;
byte[] buf = new byte[8192];
while ((numRead = inputS.read(buf)) >= 0) {
edouts.write(buf, 0, numRead);
}

edouts.checkCRLFTerminator();
            edouts.flush();
           
} catch (Exception e) {
out.println("-ERR");
log.error(ExceptionUtils.getStackTrace(e));
} finally {
try {
if (inputS != null)
inputS.close();
} catch (Throwable ignore) {
}
}
}


至於 ExtraDotOutputStream 這隻程式我就不附上了，
有興趣的可以去下載 Source Code 來看

JAVA POP3 Server 實作

※2014/09/01 JAVA POP3 Server 信件內文中斷符號問題修正

這篇可能有點長，主要是利用Java ServerSocket實作POP3 Server

當然免不了要先看一下什麼是 POP3 

接著就必須要瞭解 RFC 規範
基本上要看的就是 RFC1939 與 RFC2449 這兩份文件

RFC1939
第三點 Basic Operation (基本操作)，這是必看的，裡面有講那很多規定
例如：POP3 service by listening on TCP port 110.  Commands 不分大小寫. 參數長度不能超過40字元. 換行符號必須是CRLF.....等等

POP3 session 的三個狀態在基本操作也有說明
AUTHORIZATION State
TRANSACTION State
UPDATE State

接著就是必須實作的幾個指令
USER
PASS
STAT
LIST
RETR
DELE
NOOP
RSET
QUIT

POP Client Commands 的範例表


接下來就看程式吧!!

public class POP3Server extends Thread {
private static final Logger log = Logger.getLogger(POP3Server.class);
private static final int SERVER_PORT = 110;
private static final int MAX_CLIENT = 500;
private ServerSocket listenSocket = null;

public static void main(String[] args) {
POP3Server server = new POP3Server();
server.start();
}

public POP3Server() {
try {
listenSocket = new ServerSocket(SERVER_PORT, MAX_CLIENT);
} catch (IOException excpt) {
log.error("Sorry to open port " + SERVER_PORT + ":" + excpt);
System.exit(1);
}
}

public void run() {
Socket clientSocket = null;
try {
while (true) {
clientSocket = listenSocket.accept();
int numThreads = Thread.activeCount();
log.info(numThreads);
manageconnection newhandle = new manageconnection(clientSocket);
Thread newhandlethread = new Thread(newhandle);
newhandlethread.start();
log.info("hello");

}
} catch (IOException excpt) {
log.error("Sorry ,Failed I/O:" + excpt);
}
}
}

/* follow is manage and process command class */

class manageconnection implements Runnable {
private static final Logger log = Logger.getLogger(manageconnection.class);
private static final boolean AUTOFLUSH = true;
private Socket mySocket = null;
private PrintWriter out = null;
private BufferedReader in = null;
private long totalsize = 0;
private String username = null;
private List
private Set delMark = new HashSet();

public manageconnection(Socket newSocket) {
mySocket = newSocket;
}

public void run() {
String nextline = null;
int check = 0;
String command = null;
String arg1;
try {
Thread.currentThread();
Thread.sleep(10);
} catch (Exception e) {
log.error(e);
}
try {
mySocket.setTcpNoDelay(true);
} catch (SocketException excpt) {
log.error(excpt);
}
try {
System.setProperty("line.separator", "\r\n");
out = new PrintWriter(mySocket.getOutputStream(), AUTOFLUSH);
in = new BufferedReader(new InputStreamReader(
mySocket.getInputStream())

);
out.println("+OK" + " PoWei's pop3 server");
try {
while (true) {
if (check != 3) {
try {
nextline = in.readLine();
} catch (Exception excpt) {
log.error("sorry:" + excpt);
break;
}
log.info("C: " + nextline);

if (nextline.length() < 4) {
out.println("-ERR");
} else {
command = nextline.substring(0, 4);

switch (command.toUpperCase()) {
case "CAPA":
out.println("+OK Capability list follows");
out.println("USER");
out.println("PASS");
out.println("STAT");
out.println("QUIT");
out.println("LIST");
out.println("RETR");
out.println("DELE");
out.println("UIDL");
out.println("NOOP");
// out.println("TOP");
out.println(".");
break;
case "USER":
if (check == 0) {
check = 1;
if (nextline.length() < 5) {
out.println("-ERR");
} else {
arg1 = nextline.substring(5);
username = arg1;
out.println("+OK Password required for "
+ username);
}
} else {
out.println("-ERR");
}
break;
case "PASS":
if (check == 1) {
if (nextline.length() < 5) {
out.println("-ERR");
} else {
arg1 = nextline.substring(5);
if (check(username, arg1)) {
check = 2;
mList = readmail(username);
out.println("+OK " + username
+ " has " + mList.size()
+ " messages");
} else {
out.println("-ERR sorry auth failed");
check = 0;
}
}
} else {
out.println("-ERR");
}
break;
case "STAT":
if (check == 2) {
mList = readmail(username);
out.println("+OK" + " " + mList.size()
+ " " + totalsize);
} else {
out.println("-ERR");
}
break;
case "QUIT":
out.println("+OK BYE BYE welcome to PoWei's Mail System next time");
if (check == 2) {
if (!deleteMail(delMark)) {
out.println("-ERR some deleted messages not removed");
}
}
check = 3;
break;
case "LIST":
if (check == 2) {
out.print("+OK ");
out.println(mList.size() + " messages ("
+ totalsize + " byte)");
for (int j = 1; j <= mList.size(); j++) {
out.println(j + " "
+ mList.get(j - 1).get("size"));
}
out.println(".");
} else {
out.println("-ERR");
}
break;
case "RETR":
if (check == 2) {
if (nextline.length() < 5) {
out.println("-ERR");
} else {
arg1 = nextline.substring(5);
out.println("+OK");
log.info(arg1);
printMail(Integer.valueOf(arg1));
out.println(".");
boolean st = out.checkError();
log.info(st);
}
} else {
out.println("-ERR");
}
log.info("retr finished");
break;
case "DELE":
if (check == 2) {
if (nextline.length() < 5) {
out.println("-ERR");
} else {
arg1 = nextline.substring(5);
try {
Integer index = Integer
.valueOf(arg1) - 1;
if (!delMark.contains(index)) {
delMark.add(index);
out.println("+OK message "
+ arg1 + " deleted");
} else {
out.println("+ERR message "
+ arg1
+ " already deleted");
}

} catch (Exception e) {
out.println("-ERR");
}
}
} else {
out.println("-ERR");
}
break;
case "UIDL":
if (check == 2) {
if (nextline.length() < 5) {
out.println("+OK");
for (int j = 1; j <= mList.size(); j++) {
out.println(j
+ " "
+ mList.get(j - 1).get(
"uid"));
}
out.println(".");
} else {
Integer index = null;
try {
index = Integer.valueOf(nextline
.substring(5));
out.print("+OK ");
out.println(index
+ " "
+ mList.get(index - 1).get(
"uid"));
out.println(".");
} catch (IndexOutOfBoundsException e) {
out.println("-ERR IndexOutOfBoundsException:"
+ index);
} catch (NumberFormatException e) {
out.println("-ERR " + index);
}
}
} else {
out.println("-ERR");
}
break;
case "NOOP":
if (check == 2) {
out.println("+OK");
}
break;
case "TOP":
if (check == 2) {
out.println("+OK");
} else {
out.println("-ERR");
}
break;
default:
out.println("-ERR");
break;

}
}
} else {
out.close();
in.close();
mySocket.close();
break;
}

}
} catch (NullPointerException excpt) {
log.error("sorry " + excpt);
in.close();
out.close();
mySocket.close();
}

} catch (IOException excpt) {
log.error("Failed I/O:" + excpt);
}

log.info("bye");

}

private boolean deleteMail(Set delMark) {
boolean value = true;

for (Integer index : delMark) {
try {
Map map = mList.get(index);
if (map != null) {
//TODO remove mail
}

} catch (Exception e) {
value = false;
}
}

return value;
}

private void printMail(Integer index) {
String str = "";
GridFSDBFile gfsdbf = glist.get(index - 1);
InputStream inputS = null;
BufferedReader reader = null;
try {
inputS = gfsdbf.getInputStream();
reader = new BufferedReader(new InputStreamReader(inputS));

while ((str = reader.readLine()) != null) {
out.println(str);
}

} catch (Exception e) {
log.error(ExceptionUtils.getStackTrace(e));
} finally {
try {
if (inputS != null)
inputS.close();
if (reader != null)
reader.close();
} catch (Throwable ignore) {
}
}
}

/* check your username and password */
private boolean check(String username, String password) {
//TODO auth

return false;
}

private List
//TODO load mail

List

return ret;
}

}