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Subject: ares_fds returning zero FDs

ares_fds returning zero FDs

From: Jijo Xavier <>
Date: Fri, 17 Jun 2016 20:20:28 +0000

I use c-ares library to look up the hostname for a given IP address. Following is the sequence of operations in my code.

  1. Call ares_init to initialize the channel
  2. Call ares_gethostbyaddr, passing all the required arguments including the callback
  3. Define my fd_set and FD_ZERO it
     * fd_set readers; FD_ZERO(&readers);

  4. Call ares_fds to get the FDs that I can wait

Everything works fine almost all the time. But occasionally I ares_fds() function returns zero. No callback function is invoked. No other way of tracking what went wrong.

Is this expected ? What does it mean ? Should I treat it as an error ?


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Received on 2016-06-18