VBA XMLHTTP POST Upload text/xml File to API Service - vba

Question

I need to send XML file to API service with use of Excel/VBA.
Instructions available in documentation state that the only required field is:
file: string($binary) - file to upload. The name can be specified in the filename parameter of the Content-Disposition header.
This is the equivalent of CURL based on documentation:
curl -X 'POST' \
'api_service_url' \
-H 'accept: */*' \
-H 'Authorization: Bearer XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX=' \
-H 'Content-Type: multipart/form-data' \
-F 'file=#VPRT9000004726.xml;type=text/xml'
I have searched the web and cannot find a working solution. I am wondering, if this is something possible to do with Excel VBA XMLHTTP library at all?
Available documentation of API service can be found on this link under the UPLOAD section:
https://testapi.valenciaportpcs.net/messaging/swagger/index.html
Any help or direction appreciated.
Code that is working for uploading the file, but having issues with UTF-8 special characters:
Option Explicit
Sub UploadFile()
Dim sFile As String
Dim sUrl As String
Dim sAccessToken As String
Dim sBoundary As String
Dim sResponse As String
sFile = "D:\VPRT9000004726.xml"
sUrl = "https://testapi.valenciaportpcs.net/messaging/messages/upload/default"
sBoundary = "---------------------------166096475834725259111917034354"
sAccessToken = "myaccesstoken"
sResponse = pvPostFile(sUrl, sFile, sBoundary, sAccessToken)
'Debug.Print sResponse
End Sub
Private Function pvPostFile(sUrl As String, sFileName As String, sBoundary As String, sAccessToken As String) As String
Dim xmlReq As MSXML2.ServerXMLHTTP60
Dim nFile As Integer
Dim baBuffer() As Byte
Dim sPostData As String
'--- read file
nFile = FreeFile
Open sFileName For Binary Access Read As nFile
If LOF(nFile) > 0 Then
ReDim baBuffer(0 To LOF(nFile) - 1) As Byte
Get nFile, , baBuffer
sPostData = StrConv(baBuffer, vbUnicode)
End If
Close nFile
'--- prepare body
sPostData = "--" & sBoundary & vbCrLf & _
"Content-Disposition: form-data; name=""file""; filename=""" & Mid$(sFileName, InStrRev(sFileName, "\") + 1) & """" & vbCrLf & _
"Content-Type: text/xml" & vbCrLf & vbCrLf & _
sPostData & vbCrLf & _
"--" & sBoundary & "--"
'Debug.Print sPostData
'--- post
Set xmlReq = New MSXML2.ServerXMLHTTP60
With xmlReq
.Open "POST", sUrl, False
.setRequestHeader "Authorization", "Bearer " & sAccessToken
.setRequestHeader "Content-Type", "multipart/form-data; boundary=" & sBoundary
.setRequestHeader "Accept-Charset", "UTF-8"
.send pvToByteArray(sPostData)
pvPostFile = .Status
End With
Set xmlReq = Nothing
End Function
Private Function pvToByteArray(sText As String) As Byte()
pvToByteArray = StrConv(sText, vbFromUnicode)
End Function