OAuth 2.0 401 Unauthorised error. please answer me.

[ChokPuttaraksa]

Sorry for this Question, I've been stucking in this problem for so long. I use the OAuth 2.0 Tutorial page, I use Client ID and Client Secret from my app. And use server as http://localhost:3000/ from nodejs.

Then I clicked the link in your url in your website, I allowed that access and then I got the 401 error.

I used the code that I got from URL.

I want to know that why It's always errored 

Sorry for my incorrect Grammar. And Thank you for ur answer.

I get the answer now. Sorry for the trouble.

[JeremiahFitbit]

Where is the "Cannot GET /?code=..." error from?

[ChokPuttaraksa]

I got the solution now. It's my fault that used wrong redirect url. Thank you and sorry with this trouble.