At the company I'm working we connect to the internet using a proxy.
Because we moved from a local TFS server to Visual Studio Team System (VSTS), former known as Visual Studio Online, we need Jenkins to get source code from that.

But the TFS-plugin doesn't take into account the system proxy settings, resulting into a timeout. (see attachment).

The C# TFS API allows for setting proxy settings.
More details here: https://github.com/FubarDevelopment/restsharp.portable/issues/34

Something like this might resolve this issue.