Jenkins - Can't download upgrades / plugins - Proxy is already set - Able to reach .hpi via http fine in IE - jenkins

Question

I got the Windows Native .zip from Jenkins site and installed Jenkins on my machine (Win 7) as Windows service.
The nice dashboard is up and now I want to download some plugins / even upgrade the version (First) as I got the .zip few weeks back.
When I tried to upgrade / download the plugins (under Manage Jenkins), I'm getting the following error messages, any idea what I could be missing.
Under Plugin's ADVANCE tab, I have provided the proxy server and port. Another point I noticed that when I'm downloading a plugin (and it fails) showing the link to the plugin .hpi file, if I use that "http ://../../.hpi" in Internet Explorer, it pops up fine (telling me to open/save etc) so in one sense, I'm able to reach the .hpi file directly. I can download the .hpi file manually and put it under the Jenkins installation/..respective/../../folder and restart Jenkins service everytime I install a new/replace an existing .hpi, but that I dont want to do that.
Installing Plugins/Upgrades
Preparation
Checking internet connectivity
Checking update center connectivity
java.net.ConnectException: Connection refused: connect at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.PlainSocketImpl.doConnect(Unknown Source) at java.net.PlainSocketImpl.connectToAddress(Unknown Source) at java.net.PlainSocketImpl.connect(Unknown Source) at java.net.SocksSocketImpl.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at java.net.Socket.connect(Unknown Source) at sun.net.NetworkClient.doConnect(Unknown Source) at sun.net.www.http.HttpClient.openServer(Unknown Source) at sun.net.www.http.HttpClient.openServer(Unknown Source) at sun.net.www.http.HttpClient.(Unknown Source) at sun.net.www.http.HttpClient.New(Unknown Source) at sun.net.www.http.HttpClient.New(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source) at hudson.model.UpdateCenter$UpdateCenterConfiguration.testConnection(UpdateCenter.java:860) at hudson.model.UpdateCenter$UpdateCenterConfiguration.checkUpdateCenter(UpdateCenter.java:709) at hudson.model.UpdateCenter$ConnectionCheckJob.run(UpdateCenter.java:1030) at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)
jenkins.war
Failure -
hudson.util.IOException2: Failed to download from http://updates.jenkins-ci.org/download/war/1.508/jenkins.war
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:782)
at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:1123)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1101)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.ConnectException: Connection refused: connect
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection$6.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.protocol.http.HttpURLConnection.getChainedException(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:752)
... 8 more
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.<init>(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(Unknown Source)
at java.net.URLConnection.getHeaderFieldInt(Unknown Source)
at java.net.URLConnection.getContentLength(Unknown Source)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:751)
... 8 more
Preparation
Checking internet connectivity
Checking update center connectivity
java.io.IOException: Server returned HTTP response code: 403 for URL: http://updates.jenkins-ci.org/update-center.json?uctest at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source) at hudson.model.UpdateCenter$UpdateCenterConfiguration.testConnection(UpdateCenter.java:860) at hudson.model.UpdateCenter$UpdateCenterConfiguration.checkUpdateCenter(UpdateCenter.java:709) at hudson.model.UpdateCenter$ConnectionCheckJob.run(UpdateCenter.java:1030) at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)
Timestamper
Failure -
hudson.util.IOException2: Failed to download from http://updates.jenkins-ci.org/download/plugins/timestamper/1.5.3/timestamper.hpi
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:782)
at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:1123)
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:1285)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1101)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: Server returned HTTP response code: 403 for URL: http://updates.jenkins-ci.org/download/plugins/timestamper/1.5.3/timestamper.hpi
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection$6.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.protocol.http.HttpURLConnection.getChainedException(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:752)
... 9 more
Caused by: java.io.IOException: Server returned HTTP response code: 403 for URL: http://updates.jenkins-ci.org/download/plugins/timestamper/1.5.3/timestamper.hpi
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(Unknown Source)
at java.net.URLConnection.getHeaderFieldInt(Unknown Source)
at java.net.URLConnection.getContentLength(Unknown Source)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:751)
... 9 more

Answer 1

Since our update center server does not do any authentication and therefore never returns 403, most likely the 403 error is returned by your HTTP proxy. If I were you, I'd check the proxy user name and the password.
We should probably add a connectivity check button in the configuration page where you enter the proxy details. If you'd be so kind to file this as a ticket in https://issues.jenkins-ci.org/, I'd be happy to get to that.

Answer 2

Thanks Kohsuke. Issue was I was using the proxy hostname with http://proxyservername.com.
When I put "proxyservername.com", it worked. I'll open a ticket to get that "Test" Proxy connection button in. Would have been nice if (?) shows an example, but my bad.