The JMXMP connector is creating at least one "JMX server connection timeout Thread-*" thread in server for each client connection. From the specs of the generic connector, these threads, which check and close a connection after it's been idle for more than a specified timeout, can be avoided if we specify a timeout value equal to Long.MAX_VALUE:

Map<String, Object> env = new HashMap<>();
env.put("jmx.remote.x.server.connection.timeout", Long.MAX_VALUE);