>> Is it possible that that kernel considers binding to an IPv6 port to
>> conflict with binding to the "same" port number as an IPv4 port?
Actually, I think that that may be expected behavior depending on the
vintage of the kernel. Note the following comment in
StreamServerPort():
/*
* Note: This might fail on some OS's, like Linux older than
* 2.4.21-pre3, that don't have the IPV6_V6ONLY socket option, and
* map ipv4 addresses to ipv6. It will show ::ffff:ipv4 for all
* ipv4 connections.
*/
regards, tom lane