D:\Program Files (x86)\Jenkins\tools>java -jar jenkins-cli.jar -s http://myservername:8080/ -auth myusername:mypassword help
java.io.IOException: Server returned HTTP response code: 401 for URL: http://myservername:8080/cli?remoting=false
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
        at hudson.cli.FullDuplexHttpStream.<init>(FullDuplexHttpStream.java:72)
        at hudson.cli.CLI.plainHttpConnection(CLI.java:279)
        at hudson.cli.CLI._main(CLI.java:271)
        at hudson.cli.CLI.main(CLI.java:83)