Having set up a simple privval.SignerServer using a FilePV across a UNIX connection, I'm getting lots of messages like these in the logs:

E[2020-09-17|12:02:46.336] SignerServer: handleMessage                  err="unknown msg: <nil> ({<nil>})"
E[2020-09-17|12:02:46.436] SignerServer: handleMessage                  err="unknown msg: <nil> ({<nil>})"
E[2020-09-17|12:02:46.536] SignerServer: handleMessage                  err="unknown msg: <nil> ({<nil>})"

These appear to be caused by signerEndpoint.ReadMessage() using a read deadline with a very low timeout (~100ms), and returning an empty message when the deadline triggers. This in turn causes it to send an error response. Dropping this empty message causes the entire privval connection to stall.