Hello,
I just bought Nim in Action a few days ago and was following the ChatApp exercise and couldn't compile the clients.nim on Windows. It looks like when I
import asyncdispatch
and compile it with --threads:on I get error: redefinition of 'struct ip_mreq'. I think the problem can be fixed by reorganizing the #includes in the generated nimcache\stdlib_asyncdispatch.c to the way the answer suggests on https://stackoverflow.com/questions/1372480/c-redefinition-header-files-winsock2-h, but I'm not familiar with the process.