You need in-the-middle boxes that support both IPv4 and IPv6 and some way to translate or proxy. End-to-end communication between different protocols is not possible.
For example, if a web server is IPv6-only then an external reverse (layer 7) proxy with IPv4 and IPv6 could accept requests over IPv4 and proxy them to the IPv6 server. You could also do something similar with a box that does IP/ICMP Translation on layer 3.
And then both the IPv6 address of the server and the IPv4 address of the reverse proxy or translator should be advertised in DNS.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…