I also faced the same problem while working with eclips Neon. It got fixed after editing the .ini file with following content:
> -Dhttp.proxyPort=8080
> -Dhttp.proxyHost=myproxy
> -Dhttp.proxyUser=mydomain\myusername
> -Dhttp.proxyPassword=mypassword
> -Dhttp.nonProxyHosts=localhost|127.0.0.1
> -Djava.net.preferIPv4Stack=true
Note: Sometime it may also caused due to the issue with your Network configuration and device. So conform first that your windows firewall is allowing to connect your eclips to the outer world (internet). (Turn off the windows firewall for the instance of time that your computer take to install the file).