@Ashfaq Cloudera Manager server which is cloudera-scm-server with pckg name cloudera-manager-server-5.16.2-1.cm5162.p0.7.el7.x86_64 (5.16.2 is the version here) running behind the scenes which enables the jetty server and provide you a Web UI.
So if cloudera-scm-server service is down your CM Web UI is down. This is the short answer.
Cheers!
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