Keycloak port 39008 and port scan

Question

I did a port scan using nmap on my machine running Keycloak and was surprised to find that port 39008 was open. According to nmap:

39008/tcp open  unknown

Using the following two commands I found that it is keycloak:

netstat -tulpn | grep 39008
tcp        0      0 0.0.0.0:39008           0.0.0.0:*               LISTEN      17270/java   

ps -Af | grep 17270
me     17270 17223  0 Dec22 ?        00:13:05 java ...-Djboss.home.dir=/.../keycloak-2.4.0.Final 

I cannot find any reference to this port in the config or the docs.

What is this port used for?