Getting "underlying connection was closed" on HttpWebRequest

I have an application written in VB.NET (NOT asp.net, it is a Windows Console app). I am trying to call a url (an html page) and get back the response into a string. The response is straight JSON, no html tags whatsoever. It opens with { and closes with }.

I create the HttpWebRequest object fine. Then call req.GetResponse(). As soon as I do this I get the error The underlying connection was closed: The connection was closed unexpectedly. I've been googling and checking stackoverflow, and tried everything I've found that applies (a lot of it has to do with WCF service configurations, which don't apply).

Here is my code:

Public Function GetJSON(ByRef d As db.Device) As Boolean
    Try
        d.Url = "http://" & d.IpAddress & ini.doc.<svc>.<url>.Value

        Dim req As HttpWebRequest = HttpWebRequest.Create(d.Url)
        // req.Accept = "*/*"
        // req.Timeout = 30000
        // req.ReadWriteTimeout = 30000
        // req.KeepAlive = False
        // req.UseDefaultCredentials = True
        // req.CachePolicy = HttpWebRequest.DefaultCachePolicy
        // req.Proxy = HttpWebRequest.DefaultWebProxy
        // req.ProtocolVersion = New System.Version(1, 0)

        Dim rsp As HttpWebResponse = req.GetResponse()

        Return True
    Catch ex As Exception
        Log(ex.Message)
        Return False
    Finally
        rsp = Nothing
        req = Nothing
    End Try
End Function

The commented out lines (wrong comment style, but so SO will parse it right) are all the things I have tried so far based on what I've found online. None of them fixed it. I have verified that the URL being built is correct; if I call the exact same URL in my browser it gives back exactly the right expected response.

I've tried wiresharking it... and i see the actual expected, complete data come back in the shark output, and then a few