Hello!
Just use this to bypass https firewall rule.
https://mcuoneclipse.com/2014/07/03/replicating-an-eclipse-update-site-for-offline-usage/
eclipsec.exe -application org.eclipse.equinox.p2.metadata.repository.mirrorApplication -source http://download.gna.org/eclox/update -destination c:\temp\Mirror_Eclox
eclipsec.exe -application org.eclipse.equinox.p2.artifact.repository.mirrorApplication -source http://download.gna.org/eclox/update -destination c:\temp\Mirror_Eclox