I have 1 main user in a forum , I want to present at the forum A user can log on all BCDE forum . Through researching, I found the addon : Single Sign On ( Master ) by Waindigo or Single Sign On ( Slave ) by Waindigo But when the setup is as follows : I used to add on Master site is : 1.mydomain.com Addd on Slave to the secondary site is : 2.mydomain.com 3.mydomain.com 3 cũng This site has the same id and password . Look forward to hearing from you . In the report server error in admin cp 2.mydomain.com forum : Exception : Failed HttpRequest , url : https://1.mydomain.com/index.php?sync/sync , curl error ( 35 ) : error : 140770FC : SSL routines : SSL23_GET_SERVER_HELLO : unknown protocol - library / Waindigo / XenSso / Slave / Sync.php : 346 Generated By : Vu Thanh Phong , Yesterday at 7:26 PM exception : - Unexpected result : false - library / Waindigo / XenSso / Slave / ControllerAdmin / Sync.php : 78 Generated By : Vu Thanh Phong , When I entered : Admin CP > Tool > Xen SSO > Synchronize Users it as image below error message : I pm Waindigo not getting help from your mind. Sorry for my English degree. Thanks and best regards !