Hello cywin guru, Maybe you can help me with the following problem. We are running Cygwin version 1.3.10 on Windows NT. We use sigaction to redirect the SIGIO signal to our own signal handler in a client/server app. When running several processes of the same client program in the background, a couple of them seem to hang. It is interesting that this problem does not surface when we have all those processes running in the foreground or when we start them using "cmd start /high ..." Please find attached the relevant code for reproducing the problem. It is a client program that tries to connect to a telnetd. It expects the machine name where telnetd is running as well as the repeat count for the send loop. I reproduced the problem as follows 1. opened an xterm with a bash 2. in the xterm I typed the following for i in 1 2 3 do ./a.exe localhost 300 & done The result was that one process did well, but the other two hanged. Is this behavior related to a known CYGWIN problem? Do you think we can change our code in some way to avoid this problem? We will greatly appreciate your expert advice on this matter. Greetings, Ivan