NullRecv simply loops, receiving and discarding messages, until the Endpoint returns back a nil message. This allows the Endpoint to notice a dropped connection. It is intended for use by Protocols that are write only -- it lets them become aware of a loss of connectivity even when they have no data to send.
pe.w.Add() go pe.peerSender() go mangos.NullRecv(ep) }
x.w.Add() go x.sender(pe) go mangos.NullRecv(ep) }