What causes SignalR WebSocketException - reached the end of the file?

We are using Microsoft.AspNet.SignalR Version=2.1.1.0 running on Windows Server 2016, IIS 10. We see the following errors in the server logs -

SignalR.Transports.WebSocketTransport Error: 0 : OnError(1531b342-8587-4082-a027-b57505e29a8d, System.Net.WebSockets.WebSocketException (0x80070026): Reached the end of the file at System.Web.WebSockets.WebSocketPipe.<>c__DisplayClass9_0.b__0(Int32 hrError, Int32 cbIO, Boolean fUtf8Encoded, Boolean fFinalFragment, Boolean fClose)

What could be the cause of above error?