Hi @ken.chou

The meaning of session expiration specifically refers to the access token you acquire expiring.

When using Version 2 authentication, you are required to acquire an access token from the platform using your client credentials. This access token is used to provide safe access to the streaming data services, but will eventually expire. With version 2, so long as you remain connected, the streaming server will allow you to continue to use your access token for days, weeks, however long you remain connected. However, if you disconnect from the server, you may need to refresh your access token if it has expired. Here is a scenario:

1. You start your application and acquire an access token from the authentication server. The response will also provide an expiration time for this token.

2. When you connect into your streaming server, you will need to login using the access token. Once logged in, you can begin requesting data.

3. If you disconnect from the streaming server and the "expiration time" has not expired, you can login using your original access token. If the "expiration time" has expired, you will need to acquire a new access token and use this to login to the streaming server.

Hope this makes sense.