Thanx David.Yes the SDI app is OK!!

Hi,I found the reason. In OnReceive,I used a fixed length buffer to call Receive function,But in fact,sometimes the incoming data's length is great than the buffer length.So there was some data remained in system buffer,and the app didnt get them,I think it made OnReceive not be called anymore. Thanx everybody's advice!!

Did it help? > The problem with computers is that they do what you tell them to do and not what you want them to do. < > "It doesn't work, fix it" does not qualify as a bug report. < > Amazing what new features none of the programmers working on the project ever heard of you can learn about when reading what the marketing guys wrote about it. <

You are welcome :) Regards. -------- M.D.V. ;) If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about? Help me to understand what I'm saying, and I'll explain it better to you Rating helpfull answers is nice, but saying thanks can be even nicer.

I resovled this problem.The sample number of output pin is not enough! I increased the number from 100 to 4000,and the COutputQueue object's list cache from 10 to 1024*1024.Now everything runs well.