The option of ipappend 1 in the default file and retransmission of HELLOs in udp-sender (--rexmit-hello-interval) has been valuable to getting udpcast working with the Dell notebooks we have with Broadcom 5700 series ethernet.
Today, with a slightly newer broadcom chipset appearing in the most recent shipment, we noticed that udp-receiver was intermittantly not showing the "hit any button to start transfer" message. With some trial and error I found that if I watched the tail of /var/log/message on the receiver (server) and waited for the messages on TX and RX flow control to complete before running udp-receiver, it would always initiate a good connection. If I had started the udp-receiver prior to the TX/RX flow control appearing in the message log (in which case there was no "hit any key" message), I could ^C the receiver, run it again and it would signify the ready state with 100% success.
In conclusion, we have a workaround of starting udp-receiver after a few seconds past the client PXE machine booting and showing the udp-sender status ready (but not yet "hit any key..."). Another solution would be if udp-receiver also supported --rexmit-hello-interval. It isn't a flaw in the udpcast system but a kludge for a network device that is proving itself to be sluggish in initialization in general.
--Donald Teed