Re: connect(2) for UDP

2008/12/15 James K. Lowden <[email protected]>:
> Hello Frediano!
>
>        /*
>         * Request the instance's port from the server.
>         * There is no easy way to detect if port is closed so we always try to
>         * get a reply from server 16 times.
>         */
>        for (num_try = 0; num_try < 16; ++num_try) {
>
> But there is an easy way: use connect(2) and write(2) instead of sendto!
> connect(2) sets errno to ECONNREFUSED if no one is listening to the port,
> even for UDP.
>
> This would let us know immediately if port 1434 is reachable, and could
> reduce our retry loop to, say, three tries.
>

Mmmm... from comments

        /*
         * on cluster environment is possible that reply packet came from
         * different IP so do not filter by ip with connect
         */

the problem is not that easy... if server has two interfaces
configured server reply from a single interface so it can happen that
client ask to an interface with a given IP but server reply from
another IP, in such situation with connect used recv don't receive
server reply :( I think we can solve this problem using two sockets,
one connected and another not connected.

freddy77