Actually, as highlighted by Paul and Karl in JENKINS-63489, it might be due to your server not working properly with TLSv1.2 while P4Java uses it by default in P4 plugin 1.11.0 - it was the case for me as the version of our server is 2018.1 patch 1715250, which is older than the requirements set at 2018.1 patch 1805524 or greater.
You might want to force the TLS version to be TLSv1 as explained in https://community.perforce.com/s/article/2620. In other words, you might want to use -DsecureSocketEnabledProtocols=TLSv1 (not TLSv1.0, but TLSv1!) in your Java arguments, which for me have to be specified in %USERPROFILE%\jenkins.xml.
As I mentioned in the earlier ticket (https://issues.jenkins-ci.org/browse/JENKINS-63489?focusedCommentId=396376&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-396376), I managed to use the latest versions of Java JRE, Jenkins and P4 plugin to establish a connection that way.
It should not be necessary as explained here above, and most likely not recommended, but in case you still want to use older versions of Jenkins and P4 plugin, here is where you can find them:
Jenkins past versions:https://get.jenkins.io/war-stable/
P4 Plugin past versions:https://updates.jenkins.io/download/plugins/p4/]. To install the past version of the plugin, you need to go into Manage Jenkins > Manage Plugins > Advanced > Upload plugin and upload it.