ZeroMQ socket Recv() throws 'Context was terminated' exception - why and how to recover?

Using a ZMQ.SocketType.REP (reply) messaging socket with ZeroMQ, I am receiving messages and then sending an "OK" message back.

For now, I'm trying this locally (sending/receiving messages from the same C# console app running on the same machine).

Fairly regularly (after about 1500 messages), the line:

var receivedBytes = _recvSocket.Recv();

... will throw an exception: Context was terminated

My question is, why does this happen, and how do you recover from it?

I have a System.Threading.Thread dedicated to running my "server-side" ZeroMQ reply socket, here is the loop that it runs:

    private static void MessagingLoopReceive(object state)    {        if (_zmqc == null)        {            _zmqc = new ZMQ.Context(1);        }        _recvSocket = _zmqc.Socket(ZMQ.SocketType.REP);        _recvSocket.Bind("tcp://*:5556");        while (true)        {            if (_queueStop)            {                break;            }            //Console.WriteLine("Server blocking for receive...");            var receivedBytes = _recvSocket.Recv();            if (receivedBytes != null && receivedBytes.Length > 0)            {                //Console.WriteLine("Server message received from client, sending OK");                _recvSocket.Send("OK", Encoding.ASCII);                //Console.WriteLine("Server OK sent, adding message to queue");                _queuedMessages.Enqueue(receivedBytes);            }            else            {                Thread.Sleep(1);            }        }    }