Your sample code only reflects client activity and does not emphsize UIDL or
how you would implement such a concept, nor does it say why you would want to.
The question was directed as to what approach one would take to implement
the monitoring of new/read messages at the server level. Many popular POP
servers support this concept now, and is easily proven by using common
clients on a couple of pc's. Each client will know which messages, the
previous client has read and which messages are still unread. This indicates
that the server is caching that information and presenting it to the client
requesting a LIST.
The RFC for POP version 3 states that POP is designed to house new messages
on the server until a client downloads them and ultimately deletes them. It
was not designed for enhanced mail manipulation. If you want to be elaborate
with message management, the RFC points you to IMAP.
How ever, since the RFC supports flagging a message for deletion, we can
take the opportuinity to extend the bit into a byte and use it as a tripple
state flag {New, Read, Delete}
Here is a bit of skeleton code to help illustrate my point. I hope it
helps. I realize that it is far from complete and less than optimal, but I
am sure you can glean from it, what I was trying to demonstrate and move
forward with your project.
<Serializable()> Public Enum MessageStates As Byte
[new] = 0
[read] = 1
[delete] = 2
End Enum
<Serializable()> Public Class Mailbox
Private m_MailMessages As MailMessages
Public Sub New()
m_MailMessages = New MailMessages
End Sub
Public Property Messages() As MailMessages
Get
Return m_MailMessages
End Get
Set(ByVal Value As MailMessages)
m_MailMessages = Value
End Set
End Property
Public ReadOnly Property Count() As Integer
Get
Dim TheCount As Integer
For Each mm As MailMessage In m_MailMessages
If mm.MessageSate <> MessageStates.delete Then
TheCount = TheCount + 1
End If
Next
Return TheCount
End Get
End Property
Public NotInheritable Class MailMessages
Inherits Hashtable
Public Sub New()
MyBase.New()
End Sub
Public Overloads Sub Add(ByVal MessageID As String, ByVal MessagePtr As
MailMessage)
MyBase.Add(MessageID, MessagePtr)
End Sub
Public Overloads Function ContainsKey(ByVal MessageID As String) As
Boolean
If MyBase.ContainsKey(MessageID) = True Then
If CType(MyBase.Item(MessageID), MailMessage).MessageSate <>
MessageStates.delete Then
Return True
Else
Return False
End If
End If
End Function
Public Overrides Function GetEnumerator() As
System.Collections.IDictionaryEnumerator
Return New MailMessageEnumerator(Me)
End Function
Public Overloads Sub Remove(ByVal MessageID As String)
If MyBase.ContainsKey(MessageID) = True Then
CType(MyBase.Item(MessageID), MailMessage).MessageSate =
MessageStates.delete
End If
End Sub
Default Public Overloads Property Item(ByVal MessageID As String) As
MailMessage
Get
Return CType(MyBase.Item(MessageID), MailMessage)
End Get
Set(ByVal Value As MailMessage)
MyBase.Item(MessageID) = Value
End Set
End Property
End Class
Public NotInheritable Class MailMessageEnumerator
Implements IEnumerator
Private m_Enumerable As IDictionaryEnumerator
Public Sub New(ByVal MessageTable As MailMessages)
m_Enumerable = MessageTable.GetEnumerator
End Sub
Private ReadOnly Property IEnumerator_Current() As Object Implements
System.Collections.IEnumerator.Current
Get
Return m_Enumerable.Current
End Get
End Property
Private Function IEnumerator_MoveNext() As Boolean Implements
System.Collections.IEnumerator.MoveNext
m_Enumerable.MoveNext()
End Function
Private Sub IEnumerator_Reset() Implements
System.Collections.IEnumerator.Reset
m_Enumerable.Reset()
End Sub
Public ReadOnly Property Current() As MailMessage
Get
Return CType(IEnumerator_Current, MailMessage)
End Get
End Property
Public Function MoveNext() As Boolean
m_Enumerable.MoveNext()
End Function
Public Sub Reset()
IEnumerator_Reset()
End Sub
End Class
Public NotInheritable Class MailMessage
Private m_MessageID As String
Private m_MessageState As MessageStates
Public Sub New(ByVal MessageID As String)
m_MessageID = MessageID
m_MessageState = MessageStates.[new]
End Sub
Public ReadOnly Property MessageID() As String
Get
Return m_MessageID
End Get
End Property
Public Property MessageSate() As MessageStates
Get
Return m_MessageState
End Get
Set(ByVal Value As MessageStates)
m_MessageState = Value
End Set
End Property
End Class
End Class
Public Class POPServer
Private m_Shutdown As Boolean
Private m_LoggedInUsers As Hashtable
Private m_Sessions As Hashtable
Private m_Mailboxes As Hashtable
Private Structure SessionInfo
Dim ClientSession As POPSession
Dim UserName As String
End Structure
Public Sub New()
m_Shutdown = False
m_Sessions = New Hashtable
m_Mailboxes = New Hashtable
m_LoggedInUsers = New Hashtable
End Sub
'main loop
Sub MainLoop()
Dim poplistener As System.Net.Sockets.TcpListener
poplistener = New
System.Net.Sockets.TcpListener(System.Net.IPAddress.Parse("127.0.0.1"), 5555)
'With a TCPLisener, wait for a new connection
poplistener.Start()
Do While Not m_Shutdown
'Accept any new clients out there
Dim POPClient As System.Net.Sockets.TcpClient
POPClient = poplistener.AcceptTcpClient
'We have a connection
'Pass it on
Dim ThisSessionInfo As SessionInfo
Dim ThisSession As POPSession
Dim POPThread As System.Threading.Thread
Dim SessionID As String
SessionID = System.Guid.NewGuid.ToString
ThisSession = New POPSession(Me, POPClient, SessionID)
With ThisSessionInfo
.ClientSession = ThisSession
End With
m_Sessions.Add(SessionID, ThisSessionInfo)
POPThread = New System.Threading.Thread(AddressOf
ThisSession.SessionStart)
POPThread.Start()
Loop
poplistener.Stop()
End Sub
Public Function SessionLogin(ByVal SessionID As String, ByVal UserName As
String, ByVal Password As String) As Byte()
Dim bSuccess As Boolean
'Login Validation logic here
If bSuccess Then
If Not m_LoggedInUsers.ContainsKey(UserName.ToUpper) Then
Dim SessionMap As Hashtable
SessionMap = New Hashtable
SessionMap.Add(SessionID, SessionID)
m_LoggedInUsers.Add(UserName, SessionMap)
Else
Dim SessionMap As Hashtable
SessionMap = CType(m_LoggedInUsers(UserName), Hashtable)
SessionMap.Add(SessionID, SessionID)
End If
If m_Sessions.ContainsKey(SessionID) Then
Dim ThisSessionInfo As SessionInfo
ThisSessionInfo = CType(m_Sessions.Item(SessionID), SessionInfo)
ThisSessionInfo.UserName = UserName.ToUpper
End If
Dim ThisMailbox As Mailbox
'Deserialize the mailbox
m_Mailboxes.Add(UserName, ThisMailbox)
End If
End Function
Public Function SessionRETR(ByVal SessionID As String, ByVal MessageID As
String) As Byte()
Dim bData() As Byte
Dim bSuccess As Boolean
'Validate our session
