启动steam的串流，出现如下提示：
1 | Would you like to accept secure desktop input from Steam?. |
Solved. The methods are as follows.
Suppose that you have PC A and B, your game is installed on A, and you wanna play on B. May be B is in your office and A is at your home.
On B, RDP into A.
Launch steam on both A and B. (In B, you should see "Stream" button on the game you are to play)
Click "stream" button on B. (It will fail because you will see the boring dialog box)
Press "Tab" key and choose the window of your RDP, so now you can see that on A, your game has been launched.
On A, launch cmd.exe as administrator.
type "qwinsta" and press enter, no quotes are required.
You should see the active sessions list on your A. One of them is your RDP session, with your username followed. One of them named "concole" is what your steam on B attempted to login but failed. Please remember the session ID of the former. (The ID should be an integer.)
Type "tscon SESSIONID /password:PWD /dest:console" in the cmd on A. Change SESSIONID to the number you remembered, and PWD to your normal windows user password, leave the rest intact. Press enter. (This command will attach the RDP session to the console session)
Once you pressed enter, your RDP to A will immediately disconnect. Now, back to B, on your steam game page, click "Stop" button, then click "connect" button, you are ready to remote play :)