Using the selenium plugin on jenkins to kick off a selenium hub on my machine, I created a  selenium node on a remote machine and registered with the hub. This was successful and the Selenium console  and web console confirm this.  If I  then try to run A Fitnesse test using the grid I get a "Connection Refused" exception:

---------- exception -----

java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at org.apache.http.conn.socket.PlainConnectionSocketFactory.connectSocket(PlainConnectionSocketFactory.java:75)
at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:142)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:359)
at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:381)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:237)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:111)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:72)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
at org.openqa.selenium.remote.internal.ApacheHttpClient.fallBackExecute(ApacheHttpClient.java:138)
at org.openqa.selenium.remote.internal.ApacheHttpClient.execute(ApacheHttpClient.java:86)
at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:101)
at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:73)
at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:142)
at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:600)
at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:219)
at org.openqa.selenium.remote.RemoteWebDriver.(RemoteWebDriver.java:142)
at org.openqa.selenium.remote.RemoteWebDriver.(RemoteWebDriver.java:155)
at com.britebill.qa.selenium.webdriver.Browser.openBrowser(Browser.java:158)

---------- exception -----

If I take Jenkins out of the equation and run  selenium hub on my local machine from the command line with the remote selenium node registering as before and run the same Fitnesse test it succeeds

When running via jenkins, I noticed the following message in the console when I  clicked on "Selenium Grid" from the Jenkins dashboard

WARNING: Attempt to (de-)serialize anonymous class hudson.plugins.selenium.PluginImpl$1 in file:/Users/johnog/.jenkins/plugins/selenium/WEB-INF/lib/selenium.jar; see: https://jenkins.io/redirect/serialization-of-anonymous-classes/

I am unsure if this warning is significant but would  be interested if this was a known issue