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Access dropbox file - Authentication failed because the remote party has closed the transport stream

i'm new in this type of access.
I wrote this code but i have the error in objet to recover the list of files in dropbox.

Dim token As String
token = "sl.B6........."
Dim _command As String
_command = "https://api.dropboxapi.com/2/files/list_folder"

Dim Request As HttpWebRequest
Request = HttpWebRequest.Create(_command)

Request.Method = "GET"
Request.KeepAlive = True
Request.ContentType = "application/json"
Request.UserAgent = "Mozilla/5.0 (Windows NT 6.3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36"
Request.AllowAutoRedirect = True
Request.Headers.Add("Authorization", "Bearer " & token)

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12

Dim Response As HttpWebResponse = Request.GetResponse()

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The endpoint for folder listing is RPC call style endpoint. RPC on Dropbox uses POST request and it's mandatory 'path' to be passed in JSON style to the request body. Fix your code.

Good luck.

[Cross-linking for reference: https://stackoverflow.com/questions/78875640/access-dropbox-file-the-remote-server-returned-an-error-404-not-found ]

Здравко is correct; be sure to refer to the documentation for information on how to properly construct these requests.

Thank you.

It's first time that i use this tools.

I changed the Metod in POST and insered the path ( looking other example ) but i have always error 401 not autorized.

this is new cod :

Dim _command As String
_command = "https://api.dropboxapi.com/2/files/list_folder"

Dim Request As HttpWebRequest
Request = HttpWebRequest.Create(_command)
Request.Method = "POST"
Request.KeepAlive = True
ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 Or SecurityProtocolType.Tls12 Or SecurityProtocolType.Tls11 Or SecurityProtocolType.Tls
Request.ContentType = "application/json" ' application/x-www-form-urlencoded"
Request.UserAgent = "Mozilla/5.0 (Windows NT 6.3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.154 Safari/537.36"
ServicePointManager.SecurityProtocol = CType(48, SecurityProtocolType) Or CType(192, SecurityProtocolType) Or CType(768, SecurityProtocolType) Or CType(3072, SecurityProtocolType)
Request.AllowAutoRedirect = True

Request.Headers.Add("Authorization", "Bearer " & token)

Dim payloadLiteral = "{""Path"": ""/files/list_folder""}"

Dim payload = Encoding.UTF8.GetBytes(payloadLiteral)
Request.ContentLength = payload.Length

Using dataStream = Request.GetRequestStream()
dataStream.Write(payload, 0, payload.Length)
End Using

Try
Using response = CType(Request.GetResponse(), HttpWebResponse)
Using reader = New IO.StreamReader(response.GetResponseStream())
'Return reader.ReadToEnd()
End Using
End Using
Catch ex As WebException
Using response = CType(ex.Response, HttpWebResponse)
Using reader = New IO.StreamReader(response.GetResponseStream())
Throw New Exception(reader.ReadToEnd())
End Using
End Using
Catch ex As Exception
Throw
End Try

Are you sure the access token you're using is actual one and not expired? 🧐

Also, post the received result (either error or success) so it be clear what's going on exactly..

I have generate a new token and insered in my web app.

Additional information: Error in call to API function "files/list_folder": request body: unknown field 'Path'

Yes, of course. it's case sensitive! Also, make sure the path is valid... you may start with just empty string - it's always valid.

Perfect, it looks right.

Just a question : i had my token , generate 1 or 2 days ago and that didn't work.

If i go in App console i didn't see it and o i generate again.

How is valid a token ?

should i generate a new one every time i use my web app ?

@Lukag wrote:
...
How is valid a token ?
should i generate a new one every time i use my web app ?

Access token is short lived, so you may use it for limited time - typically 4 hours or so. If you plan to rely on access token only then, Yes, you will need new every time you are using your application. There is alternative though. 😉 Take a look here for a possible way.

Hope this helps.

@Lukag For more information, refer to the following resources:

I try to read guide and to write code to obtain by code a new token.

this is the command

https://www.dropbox.com/oauth2/authorize?client_id=.....&response_type=code&token_access_type=offline

is that the right way ? becouse i have error 404 server not found

@Lukag wrote:
...
this is the command
https://www.dropbox.com/oauth2/authorize?client_id=.....&response_type=code&token_access_type=offline
...

Hm..🤔 What I wrote there is:

@Здравко wrote:
..., open a new browser window and put into address line following:
https://www.dropbox.com/oauth2/authorize?token_access_type=offline&response_type=code&client_id=<App key>
...

Does this sound like a command? 🧐

@Lukag The described there are all steps that you need to take for simplest OAuth flow. There are other options though, but most probably you don't need them, since you want long term access to a fixed account - the yours (correct me if I'm wrong).

The only thing you need to include in your code is the last step there (the one that needs to be repeated every time your access token expires and you need new one). That step is command. The previous steps are executed one time only and most probably you don't need them encoded. You may follow them as described there if only single (your) account needs to be linked. Just take from result the refresh token and also save in your code application key (client id) and application secret (client secret). 😉 That's all. If you're still not sure, the above is NOT command, it's web address that needs to be open in web browser (so the OAuth flow starts)!!!

Hope this sheds a piece of light.

PS: Keep in mind that none of credentials need to be exposed to the client web session (that would be security hole)! If you want let client side access, it's better PKCE code flow to get in use and in such a case all steps need to be encoded (so client will be able start OAuth flow and link corresponding account accordingly, not only you). In all cases you will need to avoid exposure of credentials that have nothing to do with particular web session.

Ok , that was ad address to use in browser 😞

I understood that now it's better if i generate a new token ( by API ) every time. Is it or not ?

Hm..🤔 To be honest, I don't understand what you mean. Maybe the actual question should be do you need long term access or not?! This is your design decision though. 😉

If you need a single shot (i.e. something that would be run occasionally) application for your own use only, getting access token every time might be better (and simplest) solution. In all other cases use of some form of OAuth might be better solution (my proposal is the simplest OAuth flow for long term use - it is suitable for server side applications, as your looks like according your description).

The decision is yours.

My scenario in where by web app my customer look and open his file in dropbox.

Just one form or two, just one user or two.

I think that token access should be good. However if in future my scenario will change i'll change also my code.

So , if you agree with me i'll continue on this way .

So i'll need generate a new token every time. Can i do it run time by api ?

@Lukag wrote:
... Can i do it run time by api ?

Definitely NO! API cannot self authenticate. 🙂 If that was possible, it would be a big security HOLE.

Actually, the refresh step in my description above (that you don't like) does exactly this, but it's different thing. There refresh token is used for authentication (valid refresh token). 😉

i dont understand some steps.

Duration token is 4 hours, if generate now and tomorrow i'll use it in my app , the server'll answer me that token in expired / invalid . So should i refhresh by Api ?

Do you understand that there are different tokens? 🧐

@Lukag wrote:
...
Duration token is 4 hours, if generate now and tomorrow i'll use it in my app , the server'll answer me that token in expired / invalid ...

What token do you take in mind above? 🤔

Read again entire thread here and linked resources. 👆 Don't jump over!

I understood the nonsense I was saying, I continue to study. Thank you

I thought that the token was quite alway the same.

So.. the first step i must autenticate the app / user by this :

https://www.dropbox.com/oauth2/authorize?client_id=<APP_KEY>&response_type=code

After i use https://api.dropboxapi.com/oauth2/token

Example: code flow access token request

Right ?

@Lukag Try read again the thread I linked to. There have been all steps shown. That you have posted is the thing you don't need encoded mandatory - i.e. execute by hand single time only outside your application. The last step, you skipped above, is mandatory to reside in your code. It may generate new access tokens whenever needed. I don't know how to say it more clear!

do you speak about this ?

Yes.

ok .. i'm doing all steps

when i do

curl https://api.dropbox.com/oauth2/token -d code=<received code> -d grant_type=authorization_code -u <App key>:<App secret>

answer me that u is ambiguos

chooses : -UseBasicParsing -Uri -UseDefaultCredentials -UserAgent

It is not mandatory you use curl command. You can use any other, but of course should adapt the params. Not all command have the same params set! My example (and not only) uses original curl command, not aliases that point to something else. Check what your alias points to. It looks like some shell' internal redirection that confuses you. Try another shell.

i downloaded curl.

Now i have two token and the second one never expire. Right ? id' like use always it 🙂

refresh token doesn't expire. The tokens (and the JSON at all) are not ordered, so I don't know is it second one or not (better don't rely). Navigate on base of the field name.

ty very very much.

Good morning,

a clarification : the refresh token must be used just to obtain a new token or i can use it to obtain data ( like in /list_folder ) ?

Hm..🤔 Can you recall this? 🙋🤫 Oh.. that laziness... Is it so "impossible" not to jump the things over? 🧐🤣

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