After I disabled the deprecated "Inbound TCP Agent Protocol/2" on our server but only checked in "Inbound TCP Agent Protocol/4", it seems like the Windows agent service cannot connect with JNLP4.

The log says: 

Jun 15, 2019 4:30:37 PM hudson.remoting.jnlp.Main$CuiListener errorJun 15, 2019 4:30:37 PM hudson.remoting.jnlp.Main$CuiListener errorSEVERE: The server rejected the connection: Disabled protocol:Protocol:JNLP2-connectjava.lang.Exception: The server rejected the connection: Disabled protocol:Protocol:JNLP2-connect at hudson.remoting.Engine.onConnectionRejected(Engine.java:306) at hudson.remoting.Engine.run(Engine.java:276)

Both of my master and agent machine runs  same Java version 1.8.0_77. My jenkins version is 2.176.1.

I read a post online (URL: https://issues.jenkins-ci.org/browse/JENKINS-53018?page=com.atlassian.jira.plugin.system.issuetabpanels%3Aall-tabpanel),  someone said "I managed to figure out why our machine couldn't connect with JNLP4. By default the slave.jar file on Windows is not updated automatically. After manually downloading the file and putting it in the right place our WIndows slave happily connects using JNLP4."  I can download the slave.jar, but I don't know how to deal with this slave.jar file, i.e., where i should place into, how to run to update the old slave.jar, and where is the location of old slave.jar.

I am new to Jenkins, hope someone can help me out. Much appreciate! 

Also, it would be great if that could be fixed so that everyone can disable JNLP2.