v0.5.58

• An ipv6Only listener can share a port number with an IPv4 one, and a dual-stack IPv6 bind holds both families, as on a host: the engine kept one port space, so a probe that binds 0.0.0.0 and then :: with ipv6Only on the same port got EADDRINUSE every time (Volter World's port allocator gave up after 32 attempts in the tab).