(Visual Basic 6.0) Refresh Microsoft Teams OAuth2 Access Token

Refreshes a Microsoft Teams OAuth2 access token. When an access token expires, HTTPS requests will receive a 401 status response indicating failure. When that happens, your application can run this code to refresh the access token, and then retry the request using the new access token. Refreshing an access token does not need user interaction (i.e. does not need to display a browser to have the user interactive authorize access).

For more information, see https://docs.microsoft.com/en-us/graph/auth-v2-user?context=graph/api/1.0#5-use-the-refresh-token-to-get-a-new-access-token

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' It is assumed we previously obtained an OAuth2 access token.
' This example loads the JSON access token file 
' saved by this example: Get Microsoft Teams OAuth2 Access Token

Dim jsonToken As New ChilkatJsonObject
Dim success As Long
success = jsonToken.LoadFile("qa_data/tokens/microsoft_teams.json")
If (success <> 1) Then
    Debug.Print "Failed to load APP.json"
    Exit Sub
End If

' The access token JSON looks like this:

' {
'   "token_type": "Bearer",
'   "scope": "openid profile ...",
'   "expires_in": 3600,
'   "ext_expires_in": 3600,
'   "access_token": "...",
'   "refresh_token": "...",
'   "id_token": "..."
' }

Dim oauth2 As New ChilkatOAuth2

oauth2.TokenEndpoint = "https://login.microsoftonline.com/common/oauth2/v2.0/token"

' Replace these with actual values.
oauth2.ClientId = "MICROSOFT-GRAPH-CLIENT-ID"
' This is your app password:
oauth2.ClientSecret = "MICROSOFT-GRAPH-CLIENT-SECRET"

' Get the "refresh_token"
oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

' Send the HTTP POST to refresh the access token..
success = oauth2.RefreshAccessToken()
If (success <> 1) Then
    Debug.Print oauth2.LastErrorText
    Exit Sub
End If

success = jsonToken.UpdateString("access_token",oauth2.AccessToken)
success = jsonToken.UpdateString("refresh_token",oauth2.RefreshToken)

' Save the new JSON access token response to a file.
Dim sbJson As New ChilkatStringBuilder
jsonToken.EmitCompact = 0
success = jsonToken.EmitSb(sbJson)
success = sbJson.WriteFile("qa_data/tokens/microsoft_teams.json","utf-8",0)

Debug.Print "OAuth2 token refreshed!"
Debug.Print "New Access Token = " & oauth2.AccessToken