How to Configure Eclipse Proxy Settings

Note: If installing from an external site hangs at “calculating requirements and dependencies” after following the instructions here, try unchecking the "Contact all update sites during install" box.

Beginning with Eclipse version 4.4 (Luna), special steps are needed in order for Eclipse to contact external sites (e.g. to install updates or plugins).
If when attempting to install plugins or open the Eclipse Marketplace, you receive an error stating "Proxy Authentication Required", this article is for you.

Background

The cause of the proxy error is a new set of HTTP client libraries that Eclipse uses beginning with v4.4. Removing those libraries, along with configuring Eclipse to talk to the proxy, will cause Eclipse to fall back on the JRE HTTP client libs. This should resolve the issue.

Part A: Configure Eclipse's Proxy Settings

First, you must configure Eclipse to play nice with the proxy by doing the following:

1. In Eclipse go to Window>Preferences>General>Network Connections
2. Choose Manual for the Active Provider
3. For both HTTP and HTTPS, enter the following settings:
   
   • Host: <PROXY HOST>
   • Port: <PROXY PORT>
   • User: <PROXY USERID>
   • Password <PROXY USER PASSWORD>
   Note you will need to update this each time you change your password.
4. Click OK to save your settings.

Part B: Remove Problematic Libraries

With Eclipse not running, go to Eclipse's plugins directory (e.g. C:\Program Files\Eclipse\plugins) and delete or rename the following three .jar files:

org.eclipse.ecf.provider.filetransfer.httpclient4.ssl_1.0.0.v20140528-1625.jar
org.eclipse.ecf.provider.filetransfer.httpclient4_1.0.500.v20140528-1625.jar
org.eclipse.ecf.provider.filetransfer.ssl_1.0.0.v20140528-1625.jar

After performing parts A and B above, Eclipse should be able to contact external update sites without any issues.    Notes

This information was compiled from this StackOverflow question and this bug report comment on the Eclipse bug tracker.

In addition to above 2 parts, see if https://wiki.eclipse.org/Disabling_Apache_Httpclient helps or

configure the following in eclipse.ini file.

-Djava.net.preferIPv4Stack=true
-Declipse.p2.unsignedPolicy=allow
-Dcom.sun.management.jmxremote
-Dorg.eclipse.ecf.provider.filetransfer.excludeContributors=org.eclipse.ecf.provider.filetransfer.httpclient4