Can only one GCClient be logged in at the same time with the same Steam account?

[rzjcn]

If I log into the DOTA2 GCClient using SteamKit now, I can’t open the DOTA2 client with the same account at the same time. Similarly, if I open the DOTA2 client first, SteamKit will not be able to connect to the DOTA2 GCClient.
But I remember that I have logged in at the same time before, and I have sent commands to the DOTA2 client through SteamKit.
Yes, I now want to use SteamKit to send some commands to my running DOTA2 client, such as watching the game my friend is playing. What should I do now?