http://www.berklix.com/~jhs/src/bsd/fixes/FreeBSD/src/gen/etc/services.yak-chat.REL=CURRENT.diff
By { 12.0-ALPHA8 & 12.1-RELEASE & 2018-11-06 13.0-CURRENT } 
etc/services had moved to usr.sbin/services_mkdb/services

Not needed for 6.4-RELEASE or 7.4-RELEASE
applies to 8.2-RELEASE

Why I have this I cant remember, so moved for now from 
services.yak-chat.REL=ALL.diff 
services.yak-chat.REL=8.2-RELEASE.diff

*** 13.0-CURRENT/src/usr.sbin/services_mkdb/services	Tue Nov 25 03:59:29 2008
--- new/src/usr.sbin/services_mkdb/services	Sun Nov 11 22:28:35 CET 2018
***************
*** 465,470 ****
--- 475,482 ----
  rap		256/udp
  set		257/tcp	   #secure electronic transaction
  set		257/udp	   #secure electronic transaction
+ yak-chat	258/tcp    #yak winsock personal chat
+ yak-chat	258/udp    #yak winsock personal chat
  esro-gen	259/tcp	   #efficient short remote operations
  esro-gen	259/udp	   #efficient short remote operations
  openport	260/tcp