The underlying connection was closed: An unexpected error occurred on a send.— NuGet

Question

Whilst trying to restore nuget packages I am getting the following:-

Error 1 The underlying connection was closed: An unexpected error occurred on a send.<

Answer 1

I'm seeing this issue behind a corporate proxy using Visual Studio 2015 which utilizes the new v3 API (https://api.nuget.org/v3/index.json). In my instance, it has to do with an SSL intercepting corporate proxy (BlueCoat) that doesn't know how to handle a newer cipher protocol (eg: TLS 1.2 plus some newer key exchange cipher) being negotiated by that API endpoint I believe.