Relay - What does NetworkStateMismatch mean?

When attempting to connect a client to my Relay host, I get the status code error:
Networking.Transport.Error.StatusCode.NetworkStateMismatch

The human readable translation is:
"Sending data while connecting on connection {0} is not allowed.";

What are the possible causes of this error? I get this error even when running the instance on separate machines - one is my Smartphone with WiFi disconnected, so I've ruled out bottlenecks on the same router.

 

I'm using version 1.0.2

The join code is:
private async Task JoinEvent(string q_string)
{
RelayManager.RelayJoinData joinData;

joinData = await RelayManager.JoinGame(q_string);
eventCodeText.text = "Success";
codeInputObject.SetActive(false);

//Retrieve the Unity transport used by the NetworkManager
UnityTransport transport = NetworkManager.Singleton.gameObject.GetComponent<UnityTransport>();

// Establish the allocation data to use Relay
transport.SetClientRelayData(joinData.IPv4Address, joinData.Port, joinData.AllocationIDBytes, joinData.Key, joinData.ConnectionData, joinData.HostConnectionData);

// Start this instance as the Host
bool worked = false;
worked = networkManager.StartClient();
if (worked)
eventCodeText.text = "Client established";
else
eventCodeText.text = "Client did not establish";
}

(eventCodeText is a local TextMeshPro used for real-time display without having to look at the Debug.Log results) - The "Client established" confirmation displays, but NetworkManager.ConnectedClientsList.Count doesn't change and the error occurs when trying to use a ServerRpc.

 

That makes sense, but it's revealed a different problem - the host code seems to become invalid after a short time. If I enter the code quickly and try to connect a client, the StartClient returns true but then gets no further. If I wait somewhere between 8-10 seconds, StartClient returns false. I need to figure out if there's something else I need to do to keep the connection by the host active.

This is all the host connection code. I assumed that binding happened behind the curtain, but is there something else I need here?

private async Task LaunchHost()
{
RelayManager.RelayHostData hostData;

hostData = await RelayManager.HostGame(4);
eventCodeText.text = "Code: " + RelayManager.hostCode;

roomManager.PopulateRosters();

//Retrieve the Unity transport used by the NetworkManager
UnityTransport transport = NetworkManager.Singleton.gameObject.GetComponent<UnityTransport>();

// Establish the allocation data to use Relay
transport.SetHostRelayData(hostData.IPv4Address, hostData.Port, hostData.AllocationIDBytes, hostData.Key, hostData.ConnectionData);

// Start this instance as the Host
networkManager.StartHost();

}

 

Yes, I'm getting a 6-character join code and the return value is true, confirmed by:

// Start this instance as the Host
bool worked = false;
worked = networkManager.StartHost();
if (worked)
eventCodeText.text += "\nConnected";
else
eventCodeText.text += "\nFailed";

 

Brilliant - setting isSecure to true solved the problems! SetClientRelayData and SetHostRelayData were defaulting to a false value for isSecure. Forcing to true worked.

For reference, Heartbeat Timeout MS is unchanged from the default 500.

Thanks