Service discovery failed with app based on android bluetooth chat sample

I am writing an Bluetooth game with blue tooth part based on android Bluetooth chat sample. And I have two phones to test. Here is the problem, when I connect one phone to the other, it sometimes shows the "Unable to connect device" bundle, but when I run the Bluetooth chat sample, it never shows this, so I think it is not the problem of device. Is there anyone who has studied the Bluetooth chat sample and has the same problem that would give me some help?I am writing an Bluetooth game with blue tooth