Why is JMX remote opening 3 ports?

Question

I enable a JMX remote port on my java application :

-Dcom.sun.management.jmxremote.port=1099

With netstat, I can see that it's opening 3 ports :

$> netstat -plant | grep java

tcp6  0  0 :::1099       :::*   LISTEN      10009/java      
tcp6  0  0 :::42351      :::*   LISTEN      10009/java      
tcp6  0  0 :::55704      :::*   LISTEN      10009/java 

The 1099 is the one I asked with the system property, the other one are random ports. In my case, I can see the 42351 port is used for connections with jconsole or visualvm, but I never see any established socket on the third one.

So I would like to focus my question on this third port : what is it used for ?