Jan Vroonhof <vroonhof(a)math.ethz.ch&gt; writes: I don't know how to classify the I_GETSIG/I_SETSIG ioctl's. The header says ------------------------------- #define I_SETSIG 6 /* Inform the STREAM head that the process wants the SIGPOLL signal issued. */ #define I_GETSIG 7 /* Return the events for which the calling process is currently registered to be sent a SIGPOLL signal. */ ------------------------------- and libc.info ------------------------------- - Macro: int SIGIO This signal is sent when a file descriptor is ready to perform input or output. On most operating systems, terminals and sockets are the only kinds of files that can generate `SIGIO'; other kinds, including ordinary files, never generate `SIGIO' even if you ask them to. In the GNU system `SIGIO' will always be generated properly if you successfully set asynchronous mode with `fcntl'. - Macro: int SIGPOLL This is a System V signal name, more or less similar to `SIGIO'. It is defined only for compatibility. ------------------------------- Because of the comment at I_SETSIG (*STREAM*), I guess it can be used just with streams but not with sockets. You can read in the SIGIO description, the prefered way to generate the signal is setting asynchronous mode with 'fcntl' Yes, but I have not found much information about the usage of signals in conjunction with sockets. I have grep'ed all my info-files and man-pages but have not found anything about I_[SG]ETSIG. Enrico -- eMail: enrico.scholz(a)wirtschaft.tu-chemnitz.de talk: ensc(a)ultra.csn.tu-chemnitz.de