Below is my sample code ; the Net Cats This does not work, because 'accept' fuction of the Network module blocks the whole process, unlike Haskell Standard IO functions which blocks its thread only. How did you work around with complex networked applications ? It would be very helpful if you could give us more detailed advice from your expierience.

Network.accept does not seem to be thread friendly. Then how am I going to keep my server from being blocked by accept?

I'm not sure exactly what your program is supposed to be doing, but as far as I can tell it's working fine :-) While the accept is waiting for a connection, the thread doing the accept has taken the MVar, thus blocking the other thread which is also trying to take the MVar. I think this is perhaps not what you had in mind? Cheers, Simon