Steps to reproduce:
1. Download attach project
2. Switch platform to UWP
3. Build the project
4. Open VS solution
5. Build project (Debug, x64, Local Machine)

Results: UnityWebRequest.SendWebRequest() fails if URL contains domain name and port

Reproduced with: 2018.3.0a10, 2018.2.6f1, 2018.1.9f1, 2017.4.9f1

Note: reproducible on .NET and IL2CPP backends

Workaround:

Prefixing the URL with a valid protocol will prevent the crash, e.g. "http://" or "https://"

Typically, a default protocol (http://) is automatically prefixed to the URL if one isn't specified, but in this case, using a domain and port number, the prefix isn't applied causing an unhanded exception in the WinRT API NetworkInformation::GetProxyConfigurationAsync. Specifying a fully qualified URL will prevent this.

The unhanded exception has been fixed for 2019.1.0a2, but WebRequest behavior won't be changed to automatically prefix http:// when using a URI with domain and port. This means the WebRequest URI "httpbin.org:12345" will still fail to connect while "httpbin.org" will succeed.

Regardless, it's strongly recommended to always specify a fully qualified URI for any connection (local or remote) to avoid unexpected behavior.