How to find queueKey in web chat

I write a code for web chat use.

static String queue = new String("default");
static String sessionId = null;
Message response = flexChat.request(RequestJoin.create(context.getUserId(),  context.getSecureKey(), sessionId, queue, null));

the “response” content is

‘EventStatus’ (4) attributes:
RequestResult [str] = ERROR
PartyId [int] = 0
OccurredAt [str] = “2016-07-19T09:38:28Z”
ReferenceId [int] = 3
Description:
ErrorId [str] = “8212”
Text [str] = “Queue key could not be resolved”

seems that Queue key is wrong.

How to find the right Queue key?

Thanks.

Did you configure endpoint on Chat Server application object? If no, create it and try it again