Simple replay of a pcap file from a server stream?

I want to run some tests on a client which connects to a simple server socket and receives a (unidirectional) data stream. It's pretty straightfoward - the 'server' is actually a serial-to-ethernet device outputting just a few bytes per second. But it's in a production system and I can't fiddle with it much.

So I've used tcpdump to capture some sample data from the live connection, and I'd really like something which will pretend to be the server device: ie. listen on a socket, and when it gets a connection will play back the relevant payload data from the pcap file at the same rate, but to whatever test client is making the connection.

I can write this myself, but I felt there must be something off-the-shelf which could be made to do this. I don't think, though, that tcpreplay or tcpliveplay will... anyone know anything else that might?