NIS user can not connect to NIS server

i have run an NIS service on Centos7 on a virtual machine. also i installed another Centos7 virtual machine as client. so i want to connect from my client vm to server vm. at client vm 'systemctl status ypbind' returns running. i have added some users at server but it fails to switch user at client. here is what 'yptest' command returns: [root@www ~]# yptest Test 1: domainname Configured domainname is "topipi.jp" Test 2: ypbind Used NIS server: nis.topipi.jp Test 3: yp_match WARNING: No such map in server's domain (Map passwd.byname, key nobody) Test 4: yp_first WARNING: No such map in server's domain (Map passwd.byname) Test 5: yp_next -- skipped -- Test 6: yp_master WARNING: No such map in server's domain (Map passwd.byname) Test 7: yp_order WARNING: No such map in server's domain (Map passwd.byname) Test 8: yp_maplist netid.byname group.bygid group.byname passwd.byuid passwd.byname mail.aliases protocols.byname protocols.bynumber services.byservicename services.byname rpc.bynumber rpc.byname hosts.byaddr hosts.byname ypservers Test 9: yp_all WARNING: No such map in server's domain (Map passwd.byname) 5 tests failed here is the error i get: [root@www ~]# su - Mahan su: user Mahan does not exist where Mahan is already added as a user at server. what should i do? and this is what i get when type 'yptest' at server: [root@nis home]# yptest Test 1: domainname Configured domainname is "topipi.jp" Test 2: ypbind Can't communicate with ypbind