Downloaded the Apex Dataloader 18.0. Cannot login to Dataloader and error message is "Failed to send request to https://login.salesforce.com/services/Soap/u/18.0".
1) gave proxy details (username, password, port and name) and server name details correctly.
2) gave SF username and password(with security token).
3) Following this article https://help.salesforce.com/HTViewSolution?id=000220227
tried to export the certificate, but received Keytool error: java.io.Filenotfound exception.