使用vb.net中的pop3从gmail服务器检索电子邮件

Question

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", "snshanjava@gmail.com", "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

她想要使用pop3从gmail服务器获取邮件，如果发现邮件然后在文本框中显示每个电子邮件内容并在messagebox中显示每条消息但在调试时没有错误有异常 - 类型'测试应用程序'pop3异常的例外被抛出.Myproblem是我在我的gmailaccount中有很多电子邮件，但无法检索这些电子邮件，点击事件将处理其他条件，它显示一个消息框，没有在服务器上找到电子邮件。

有人在这个问题上提供帮助。谢谢提前

Answer 1

首先，如果您不屑于阅读David Ross Goben的PDF文档，因为您发布的代码是100％他（除了您已删除的评论），您会注意到GMail，Yahoo和Hotmail等提供商需要SSL。

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.NetEMail课程中提供的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知道在没有记下他的情况下发布他的代码。

最后，如果您留下代码注释（正如David R Goben最初的那样），其他成员可以更好地理解代码，而不必考虑它。

回到你的问题。

GMail服务器上的消息有可能已被标记为“已读”，这可能意味着当您执行POP3.list时这些消息不会显示。

最好使用POP3.Statistics查看是否确实要下载消息。

如果POP3.List返回消息列表，您可以根据列表中的值获取消息，因为List保存每条消息的UID。

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消息。

**下次让人们花时间和精力为他们提供可以用于自己利益的代码。