Cannot open Eclipse Marketplace

This is most often caused by a problem with your internet connection. Please check your internet connection and retry. marketplace.eclipse.org

 First solution

1. Go to-Window->Preferences->General->Network Connections
2. Choose "Active Provider" To "Direct"
3. then click "apply" and then "ok".

 Second solution

1. Open command prompt (windows start button, type cmd in search)
2. Click top left of command prompt, click properties, enable quick edit mode
3. Copy: setx _JAVA_OPTIONS -Djava.net.preferIPv4Stack=true
4. Right click on command prompt, should paste
5. Hit enter. That easy!

Third solution

I tried all the suggestions but no success for Eclipse Mars, Neo and Oxygen At last it worked for Eclipse Oxygen when I added following line to eclipse.ini file

-Djava.net.preferIPv4Stack=true