在 vb.net 中使用 pop3 从 gmail 服务器检索电子邮件

Retrieve email from gmail server using pop3 in vb.net

提问by user3153806

Public Class Pop3
    Inherits Sockets.TcpClient
    Dim Stream As Sockets.NetworkStream
    Dim UsesSSL As Boolean = False
    Dim SslStream As Security.SslStream
    Dim SslStreamDisposed As Boolean = False
    Public LastLineRead As String = vbNullString
    Public Overloads Sub Connect(ByVal server As String, _
                             ByVal username As String, _
                             ByVal password As String, _
                             Optional ByVal inport As Integer = 110, _
                             Optional ByVal usessl As Boolean = False)
        If Connected Then disconnect()
        UsesSSL = usessl
        MyBase.Connect(server, inport)
        Stream = MyBase.GetStream()
        If UsesSSL Then
            SslStream = New Security.SslStream(Stream)
            SslStream.AuthenticateAsClient(server)
        End If
        If Not checkresponse() Then Exit Sub
        If CBool(Len(username)) Then
            Me.Submit("user" & username & vbCrLf)
            If Not checkresponse() Then Exit Sub
        End If
        If CBool(Len(password)) Then
            Me.Submit("pass" & password & vbCrLf)
            If Not checkresponse() Then Exit Sub
        End If
    End Sub
    Public Function checkresponse() As Boolean
        If Not IsConnected() Then Return False
        LastLineRead = Me.Response
        If (Left(LastLineRead, 3) <> "+ok") Then
            Throw New POP3Exception(LastLineRead)
            Return False
        End If

        Return True
    End Function
    Public Function IsConnected() As Boolean
        If Not Connected Then
            Throw New POP3Exception("Not Connected to an Pop3 Server")
            Return False
        End If
        Return True


    End Function
    Public Function Response(Optional ByVal datasize As Integer = 1) As String
        Dim enc As New ASCIIEncoding
        Dim serverbufr() As Byte
        Dim index As Integer = 0
        If datasize > 1 Then
            ReDim serverbufr(datasize - 1)
            Dim dtsz As Integer = datasize
            Dim sz As Integer
            Do While index < datasize
                If UsesSSL Then
                    sz = SslStream.Read(serverbufr, index, dtsz)
                Else
                    sz = Stream.Read(serverbufr, index, dtsz)
                End If
                If sz = 0 Then Return vbNullString
                index += sz
                dtsz -= sz
            Loop
        Else
            ReDim serverbufr(255)
            Do
                If UsesSSL Then
                    serverbufr(index) = CByte(SslStream.ReadByte)
                Else
                    serverbufr(index) = CByte(Stream.ReadByte)
                End If
                If serverbufr(index) = -1 Then Exit Do
                index += 1
                If serverbufr(index - 1) = 10 Then Exit Do
                If index > UBound(serverbufr) Then
                    ReDim Preserve serverbufr(index + 256)

                End If
            Loop
        End If
        Return enc.GetString(serverbufr, 0, index)

    End Function

    Public Sub Submit(ByVal message As String)
        Dim enc As New ASCIIEncoding
        Dim WriteBuffer() As Byte = enc.GetBytes(message)
        If UsesSSL Then
            SslStream.Write(WriteBuffer, 0, WriteBuffer.Length)
        Else
            Stream.Write(WriteBuffer, 0, WriteBuffer.Length)
        End If
    End Sub

    Public Sub disconnect()
        Me.Submit("QUIT" & vbCrLf)
        checkresponse()
        If UsesSSL Then
            SslStream.Dispose()
            SslStreamDisposed = True
        End If

    End Sub
    Public Function statistics() As Integer()
        If Not IsConnected() Then Return Nothing
        Me.Submit("STAT" & vbCrLf)
        LastLineRead = Me.Response
        If (Left(LastLineRead, 3) <> "+OK") Then
            Throw New POP3Exception(LastLineRead)
            Return Nothing
        End If
        Dim msgInfo() As String = Split(LastLineRead, " "c)
        Dim result(1) As Integer
        result(0) = Integer.Parse(msgInfo(1))
        result(1) = Integer.Parse(msgInfo(2))
        Return result

    End Function

    Public Function List() As ArrayList
        If Not IsConnected() Then Return Nothing
        Me.Submit("LIST" & vbCrLf)
        If Not checkresponse() Then Return Nothing

        Dim retval As New ArrayList
        Do
            Dim response As String = Me.Response
            If (response = "." & vbCrLf) Then
                Exit Do
            End If
            Dim msg As New Pop3Message
            Dim msgInfo() As String = Split(response, " "c)
            msg.number = Integer.Parse(msgInfo(0))
            msg.bytes = Integer.Parse(msgInfo(1))
            msg.Retrieved = False
            retval.Add(msg)
        Loop
        Return retval
    End Function

    Public Function GetHeader(ByRef msg As Pop3Message, Optional ByVal BodyLines As Integer = 0) As Pop3Message
        If Not IsConnected() Then Return Nothing
        Me.Submit("TOP " & msg.number.ToString & " " & BodyLines.ToString & vbCrLf)
        If Not checkresponse() Then Return Nothing
        msg.Message = vbNullString

        Do
            Dim response As String = Me.Response
            If response = "." & vbCrLf Then
                Exit Do
            End If
            msg.Message &= response
        Loop
        Return msg

    End Function
    Public Function Retrieve(ByRef msg As Pop3Message) As Pop3Message
        If Not IsConnected() Then Return Nothing
        Me.Submit("RETR " & msg.number.ToString & vbCrLf)
        If Not checkresponse() Then Return Nothing
        msg.Message = Me.Response(msg.bytes)

        Do
            Dim S As String = Response()
            If S = "." & vbCrLf Then
                Exit Do
            End If
            msg.Message &= S
        Loop
        msg.bytes = Len(msg.Message)
        Return msg
    End Function

    Public Sub Delete(ByVal msgHdr As Pop3Message)
        If Not IsConnected() Then Exit Sub
        Me.Submit("DELE " & msgHdr.number.ToString & vbCrLf)
        checkresponse()
    End Sub
    Public Sub reset()
        If Not IsConnected() Then Exit Sub
        Me.Submit("RSET" & vbCrLf)
        checkresponse()

    End Sub
    Public Function noop() As Boolean
        If Not IsConnected() Then Return False
        Me.Submit("NOOP")
        Return checkresponse()
    End Function

    Protected Overrides Sub Finalize()
        If SslStream IsNot Nothing AndAlso Not SslStreamDisposed Then
            SslStream.Dispose()
        End If
        MyBase.Finalize()

    End Sub
    Public Function ReadPop3(ByVal Server As String, _
                              ByVal username As String, _
                              ByVal password As String, _
                              Optional ByVal Inport As Integer = 110, _
                              Optional ByVal usessl As Boolean = False) As ArrayList
        Try
            Dim inmail As New Pop3
            inmail.Connect(Server, username, password, Inport, usessl)
            Dim stats() As Integer = inmail.statistics()
            If stats(0) = 0 Then
                Return Nothing

            End If
            Dim locallist As New ArrayList
            For Each msg As Pop3Message In inmail.List
                locallist.Add(inmail.Retrieve(msg))
            Next
            inmail.disconnect()
            Return locallist
        Catch ex As POP3Exception
            MsgBox(ex.Message, MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "Error Encounted")

        Catch e As Exception
            MsgBox(e.Message, MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation, "Error Encounted")
        End Try
        Return Nothing
    End Function

End Class
Public Class Pop3Message
    Public MailID As Integer = 0
    Public ByteCount As Integer = 0
    Public number As Integer = 0
    Public bytes As Integer = 0
    Public Retrieved As Boolean = False
    Public Message As String = vbNullString

    Public Overrides Function ToString() As String
        Return Message
    End Function
End Class

Public Class POP3Exception
    Inherits ApplicationException

    Public Sub New(ByVal str As String)
        MyBase.New(str)
    End Sub
End Class

.................................................

 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.Button1.Enabled = False
        Dim emailbag As ArrayList = getmail.ReadPop3("Pop.gmail.com", "[email protected]", "shan1986", 995, True)
        If emailbag IsNot Nothing AndAlso emailbag.Count <> 0 Then
            For Each msg As Pop3Message In emailbag
                Me.TextBox1.Text = msg.Message
                MsgBox(msg.Message, MsgBoxStyle.OkOnly, "message #" & msg.MailID.ToString & " of " & emailbag.Count.ToString)

            Next
        Else
            MsgBox("no Email found on server ", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information, "No email")
        End If

        Me.Button1.Enabled = True


    End Sub

her i want to get mail from gmail server using pop3 if mail found then display each email stuff in textbox and display each message in messagebox but while debugging no errors there was exception ---exception of type 'test application' pop3 exception was thrown.Myproblem is i have many emails in my gmailaccount but not able to retrieve those emails and click event will process else condition and it show an message box that no emails found on server.

如果找到邮件，我想使用 pop3 从 gmail 服务器获取邮件，然后在文本框中显示每个电子邮件内容并在消息框中显示每条消息，但是在调试没有错误时出现异常 --- 抛出了“测试应用程序”类型的异常 pop3 异常。我的问题是我的 gmailaccount 中有很多电子邮件，但无法检索这些电子邮件，单击事件将处理其他条件，并显示一个消息框，在服务器上找不到电子邮件。

somebody help on this issue .thanks in advance

有人帮助解决这个问题。提前致谢

回答by Tino Fourie

First off, if you bothered to read David Ross Goben's PDF document, since the code you have posted is 100% his (apart from the comments you have removed), you would have noticed that providers like GMail, Yahoo and Hotmail all require SSL.

首先，如果您费心阅读 David Ross Goben 的 PDF 文档，因为您发布的代码 100% 是他的（除了您已删除的评论），您会注意到 GMail、Yahoo 和 Hotmail 等提供商都需要 SSL。

Secondly, you can always send a message to David R Goben on his Gmail address (as listed in the PDF document you got with his .NetEMail classes), I am sure he will be happy to know about your problem and how you go about posting his code without crediting him.

其次，您可以随时通过他的 Gmail 地址向 David R Goben 发送消息（如您​​在他的 .NetEMail 类中获得的 PDF 文档中所列），我相信他会很高兴知道您的问题以及您如何发帖他的代码没有归功于他。

Lastly, if you left in the code comments (as David R Goben had it originally) other members could understand the code better without thinking about it.

最后，如果您留在代码注释中（正如 David R Goben 最初所说的那样），其他成员无需考虑就可以更好地理解代码。

Getting back to your problem.

回到你的问题。

There is a chance that the messages on the GMail server is already flagged as "Read" which could mean that these messages will not show up when you do a POP3.list.

GMail 服务器上的邮件可能已被标记为“已读”，这可能意味着在您执行 POP3.list 时这些邮件不会显示。

Best is to use the POP3.Statistics to see if there are in fact messages to be downloaded.

最好是使用 POP3.Statistics 来查看是否有实际的邮件要下载。

In the event that the POP3.List returns a list of messages, you can fetch messages based on the values in the list since the List holds the UID of each message.

如果 POP3.List 返回一个消息列表，您可以根据列表中的值获取消息，因为 List 保存着每条消息的 UID。

Another option is to stop reading your mail and allow your program to do either a POP3.Statistics and / or POP3.List to determine if there are any messages on the server.

另一种选择是停止阅读您的邮件并允许您的程序执行 POP3.Statistics 和/或 POP3.List 以确定服务器上是否有任何邮件。

**Next time credit people for the time and effort they have put into providing you with code that you can use to your own benefit.

** 下次感谢人们为您提供的代码所付出的时间和精力，您可以利用这些代码为自己谋取利益。