SCCM Client does not show up in console

Today, I come across a client which was not showing in the SCCM console and when I looked at the ccmexec.log I noticed the following error logs. 

ccmexec.log: 

[CCMHTTP] HTTP ERROR: URL=http://sccmserver.abc.com/ccm_system/request, Port=443, Protocol=https, SSLOptions=1, Code=12029, Text=ERROR_WINHTTP_CANNOT_CONNECT
HandleRemoteSyncSend failed (0x80040231).
CForwarder_Sync::Send failed (0x80040231).
CForwarder_Base::Send failed (0x80040231).

Resolution: 

Make sure the required port are opened on the firewall. In my case it was 443 and port 80 once they are opened my ConfigMgr client shown up with in 15-20 minutes in the SCCM console.