Winsock file transfer issue (through Internet only?)

[Inuya5ha]

Hi, I'm using the Winsock OCX in VB6 to create a personal file server application, and it transfer files perfectly within the LAN, but not the Internet. If I access it via localhost or the machine name over LAN, it works perfect. But when accessing via the Internet IP, only the first block of the file arrives to the user's browser. However it is entirely sent, no errors appear in the server application.

The main code to send the file is below, taken from DigiRev's Send File With Winsock code and modified to make it politely wait for the SendComplete event before sending the next chunk of data. Didn't fix the problem anyway.

Open FilePath For Binary Access Read As #lonFF
    
    ReDim bytData(1 To PacketSize) As Byte
    
    Do Until (lonSize - lonCurByte) < PacketSize
        Get #lonFF, lonCurByte + 1, bytData()
        lonCurByte = lonCurByte + PacketSize
        
        Do While sendComplete = False
            DoEvents '-- wait for the sendComplete event from winsock (using a flag)
        Loop
        
        Debug.Print SocketObject.State '-- show socket state (sckConnected)
        Debug.Print "Sending block " & lonCurByte
        
        sendComplete = False
        SocketObject.SendData bytData()
        DoEvents
    Loop
    
    lonPrevSize = lonSize - lonCurByte
    
    If lonPrevSize > 0 Then
        ReDim bytData(1 To lonPrevSize) As Byte
        Get #lonFF, lonCurByte + 1, bytData()
        lonCurByte = lonCurByte + lonPrevSize
        
        Do While sendComplete = False
            DoEvents '-- wait for the sendComplete event from winsock (using a flag)
        Loop
        
        Debug.Print SocketObject.State '-- show socket state (sckConnnected)
        Debug.Print "Sending final block..."
        
        sendComplete = False
        SocketObject.SendData bytData()
        DoEvents
    End If

Close #lonFF

Also tried with the UniSock API and the result is the same. And I used the Winsock repair utility just in case, of course it was useless. Also tried all possible block sizes: 1024, 2048, 4096, 8192... always the first block arrives to destination, and the browser keeps "Loading..." forever.

ANY help wil be greatly appreciated. I'm not sending any headers before sending the file, I've tried that but didn't fix anything. And if it works OK over LAN, why it fails when accessing the server using the Internet IP?