how to checkout project from remote xcode server

What do you mean by "a remote xcode server?" Xcode servers, per se, are only used to coordinate multiple build streams and continuous testing and integration, not source code repositories. Xcode can clone a project from a remote Git or Subversion repository. There is an entry on the screen that comes up when you first start up Xcode, "Clone Repository," or via the "Clone" menu entry under the "Source Code" main menu item. If what you mean by "Xcode server" you mean a source code repository, then you can use those Xcode commands to clone a Git or Subversion repository. And, that includes the repository of a remote Xcode project or workspace, you just need the pathname to the directory containing the .git or .svn directory.

Xcode server used to have the ability to to serve git repositories, but this capability was removed in Xcode 9.

This is documented in the Xcode 9 release notes, under the heading "Xcode Server" -> "Deprecations".