Samsung is notifying SideSync users that the service will shut down on October 15. For those of you that haven't used SideSync, it gives you control of your smartphone through a PC or Mac. Samsung has had a replacement service for SideSync, called Samsung Flow, and it will continue to operate so SideSync loyals can switch over to that one. There have been alternative services that do most of what SideSync does, like PushBullet, TeamViewer and AirDroid. Source
Source: https://www.gsmarena.com/samsung_will_shut_down_sidesync_on_october_15_samsung_flow_lives_on-news-39150.php