<p>As described in Jenkins documentation <a href="https://jenkins.io/doc/book/managing/security/#jnlp-tcp-port" rel="nofollow noreferrer">https://jenkins.io/doc/book/managing/security/#jnlp-tcp-port</a>, you need to configure:</p>

<ol>
<li>Jenkins to use fixed TCP port for JNLP agent, for instance 39057</li>
<li>AWS loadbalancer to listen on port 39057 and forward it to Jenkins on same port</li>
</ol>

CC BY-SA 4.0
2019-11-14T22:38:18.863Z
2019-11-14T22:38:18.863Z
n4rmo
<p>We've got a Linux Jenkins master node  set up in AWS behind a load balancer and I'm attempting to connect to Windows slave nodes in private subnets.  Is this possible?  The Jenkins URL is accessible when I RDP into each server, but when I attempt to configure the node using "Launch agent from browser" an error occurs.</p>

<pre><code>hudson.remoting.jnlp.Main$CuiListener status
INFO: Connecting to &lt;JenkinsURL&gt;:39057 (retrying:4)
java.io.IOException: Failed to connect to gpa-jenkins- 
prod.aws.baxter.com:39057
    at org.jenkinsci.remoting.engine.JnlpAgentEndpoint.open(JnlpAgentEndpoint.java:242)
    at hudson.remoting.Engine.connect(Engine.java:686)
    at hudson.remoting.Engine.innerRun(Engine.java:547)
    at hudson.remoting.Engine.run(Engine.java:469)
Caused by: java.net.ConnectException: Connection refused: connect
    at sun.nio.ch.Net.connect0(Native Method)
    at sun.nio.ch.Net.connect(Unknown Source)
    at sun.nio.ch.Net.connect(Unknown Source)
    at sun.nio.ch.SocketChannelImpl.connect(Unknown Source)
    at java.nio.channels.SocketChannel.open(Unknown Source)
    at org.jenkinsci.remoting.engine.JnlpAgentEndpoint.open(JnlpAgentEndpoint.java:203)
    ... 3 more
</code></pre>

<p>What could be the source for this refusal? </p>

CC BY-SA 4.0
2019-11-15T09:11:23.603Z
Could you explain why the jenkins-master does not reside in the same private subnet as well?
030
<jenkins><amazon-web-services>
Can Jenkins master connect to a slave node in a private subnet?
Franchise
# Can Jenkins master connect to a slave node in a private subnet?

(Asked by: username_0 on 2019-11-14)

We've got a Linux Jenkins master node  set up in AWS behind a load balancer and I'm attempting to connect to Windows slave nodes in private subnets.  Is this possible?  The Jenkins URL is accessible when I RDP into each server, but when I attempt to configure the node using "Launch agent from browser" an error occurs.
hudson.remoting.jnlp.Main$CuiListener status
INFO: Connecting to :39057 (retrying:4)
java.io.IOException: Failed to connect to gpa-jenkins- 
prod.aws.baxter.com:39057
    at org.jenkinsci.remoting.engine.JnlpAgentEndpoint.open(JnlpAgentEndpoint.java:242)
    at hudson.remoting.Engine.connect(Engine.java:686)
    at hudson.remoting.Engine.innerRun(Engine.java:547)
    at hudson.remoting.Engine.run(Engine.java:469)
Caused by: java.net.ConnectException: Connection refused: connect
    at sun.nio.ch.Net.connect0(Native Method)
    at sun.nio.ch.Net.connect(Unknown Source)
    at sun.nio.ch.Net.connect(Unknown Source)
    at sun.nio.ch.SocketChannelImpl.connect(Unknown Source)
    at java.nio.channels.SocketChannel.open(Unknown Source)
    at org.jenkinsci.remoting.engine.JnlpAgentEndpoint.open(JnlpAgentEndpoint.java:203)
    ... 3 more

What could be the source for this refusal?

**Tags:** jenkins, amazon-web-services

> **Comments:**
> **username_1**: Could you explain why the jenkins-master does not reside in the same private subnet as well?  

---

## 1 answers

### Answer by username_2 on 2019-11-14. Score: 1

As described in Jenkins documentation <https://jenkins.io/doc/book/managing/security/#jnlp-tcp-port>, you need to configure:

1. Jenkins to use fixed TCP port for JNLP agent, for instance 39057
2. AWS loadbalancer to listen on port 39057 and forward it to Jenkins on same port


---

