ares_process(3) Process events for name resolution


#include <ares.h>
void ares_process(ares_channel channel, fd_set *read_fds,

void ares_process_fd(ares_channel channel, ares_socket_t read_fd,


The ares_process(3) function handles input/output events and timeouts associated with queries pending on the name service channel identified by channel. The file descriptor sets pointed to by read_fds and write_fds should have file descriptors set in them according to whether the file descriptors specified by ares_fds(3) are ready for reading and writing. (The easiest way to determine this information is to invoke select with a timeout no greater than the timeout given by ares_timeout(3) ).

The ares_process function will invoke callbacks for pending queries if they complete successfully or fail.

ares_process_fd(3) works the same way but acts and operates only on the specific file descriptors (sockets) you pass in to the function. Use ARES_SOCKET_BAD for "no action". This function is of course provided to allow users of c-ares to void select() in their applications and within c-ares.


The following code fragment waits for all pending queries on a channel to complete:

int nfds, count;
fd_set readers, writers;
struct timeval tv, *tvp;
while (1)
    nfds = ares_fds(channel, &readers, &writers);
    if (nfds == 0)
    tvp = ares_timeout(channel, NULL, &tv);
    count = select(nfds, &readers, &writers, NULL, tvp);
    ares_process(channel, &readers, &writers);


Greg Hudson, MIT Information Systems
Copyright 1998 by the Massachusetts Institute of Technology.