I would able to telnet from my salve node to the master node (telnet connected:

May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main createEngine
INFO: Setting up agent: jenkins_slave
May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main$CuiListener <init>
INFO: Jenkins agent is running in headless mode.
May 07, 2018 1:26:27 AM org.jenkinsci.remoting.engine.WorkDirManager initializeWorkDir
INFO: Using /opt/jenkins/remoting as a remoting work directory
May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Locating server among https://jenkins-dev-aws.twg.co.nz/
May 07, 2018 1:26:27 AM org.jenkinsci.remoting.engine.JnlpAgentEndpointResolver resolve
INFO: Remoting server accepts the following protocols: [JNLP4-connect, Ping]
May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Agent discovery successful
Agent address: jenkins-dev-aws.twg.co.nz
Agent port: 50000
Identity: df:0a:5c:07:b1:32:51:72:60:9f:eb:61:dc:45:68:24
May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Handshaking
May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Connecting to jenkins-dev-aws.twg.co.nz:50000
May 07, 2018 1:26:27 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Trying protocol: JNLP4-connect
May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Protocol JNLP4-connect encountered an unexpected exception
java.util.concurrent.ExecutionException: org.jenkinsci.remoting.protocol.impl.ConnectionRefusalException: Connection closed before acknowledgement sent
at org.jenkinsci.remoting.util.SettableFuture.get(SettableFuture.java:223)
at hudson.remoting.Engine.innerRun(Engine.java:609)
at hudson.remoting.Engine.run(Engine.java:469)
Caused by: org.jenkinsci.remoting.protocol.impl.ConnectionRefusalException: Connection closed before acknowledgement sent
at org.jenkinsci.remoting.protocol.impl.AckFilterLayer.onRecvClosed(AckFilterLayer.java:280)
at org.jenkinsci.remoting.protocol.FilterLayer.abort(FilterLayer.java:164)
at org.jenkinsci.remoting.protocol.impl.AckFilterLayer.access$000(AckFilterLayer.java:43)
at org.jenkinsci.remoting.protocol.impl.AckFilterLayer$1.run(AckFilterLayer.java:176)
at org.jenkinsci.remoting.protocol.IOHub$DelayedRunnable.run(IOHub.java:958)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at hudson.remoting.Engine$1$1.run(Engine.java:94)
at java.lang.Thread.run(Thread.java:748)

May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Connecting to jenkins-dev-aws.twg.co.nz:50000
May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Server reports protocol JNLP4-plaintext not supported, skipping
May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Server reports protocol JNLP3-connect not supported, skipping
May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Server reports protocol JNLP2-connect not supported, skipping
May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener status
INFO: Server reports protocol JNLP-connect not supported, skipping
May 07, 2018 1:26:38 AM hudson.remoting.jnlp.Main$CuiListener error
SEVERE: The server rejected the connection: None of the protocols were accepted
java.lang.Exception: The server rejected the connection: None of the protocols were accepted
at hudson.remoting.Engine.onConnectionRejected(Engine.java:670)
at hudson.remoting.Engine.innerRun(Engine.java:634)
at hudson.remoting.Engine.run(Engine.java:469)