Different behavior in connecting to port 0 in windows 2008 32/64 bit [closed]

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Closed 9 years ago.

When I run the below code in windows 2008 32 bit server, program flow goes to sckTest_Error() when connect() is called.

But when I run the same code in windows 2008 64 bit server, RTE occurs and program flow goes to error:

Private Sub Form_Load()
On Error GoTo error1
     If (Not (Me.sckTest.State = sckConnected)) Then
        '
        'Log event for outbound client mode connectoin

        If Me.sckTest.State <> sckClosed Then
            Me.sckTest.Close
        End If
        '
        MsgBox "Going to connect"
        Me.sckTest.Connect "127.0.0.1", 0
        MsgBox "Connecting"
       If Me.sckTest.State = sckConnected Then
        MsgBox "Connected"
       End If
        '
    End If
    Exit Sub
error1:
    MsgBox "RTE " & Err.Number
End Sub


Private Sub sckTest_Error(ByVal Number As Integer, 
                          Description As String, 
                          ByVal Scode As Long, 
                          ByVal Source As String, 
                          ByVal HelpFile As String, 
                          ByVal HelpContext As Long, 
                          CancelDisplay As Boolean)
    MsgBox "Error in connecting" & Number
End Sub

But I get error as 10049 in both servers. Can any please advice its the problem with my code or server behavior.

Thanks

Answer 1

Port 0 is a special wildcard that allows a socket to bind to a random available ephimeral port. After the binding is successful, you can query the socket to discover which actual port it bound to. As such, you cannot connect a client socket to port 0, because it is not possible for a server socket to listen on port 0 in the first place.