eval {
        local $SIG{ALRM} = sub { next "timeout" };
        alarm(20);
        eval{
            $portaddr = recv(SOCKET, $id, 10000, 0) or next "recv: $!";
            ($port, $ipaddr) = sockaddr_in($portaddr);
            my $host = gethostbyaddr($ipaddr, AF_INET);
        };
        alarm(0);
    };
    alarm(0);
    next if $@ && $@ !~ /timeout/;