Error rmi.connection

[derk.hulshof]

Can someone explain this error for me?
And what is com.servoy.j2db.dataprocessing.Zb exactly doing?

I got this message since I updated the servoy server to 7.3.1

014-04-17 12:16 pool-2-thread-551 ERROR com.servoy.j2db.dataprocessing.Zb Error flushing message buffer to client D6488C70-D9E5-4E0C-9FC8-B7A8007F3798
java.rmi.ConnectException: Connection refused to host: [IPadres]; nested exception is:
java.net.ConnectException: no multiplexer found for server with id=597ec4dc-3a47-4a5f-bc7d-785c4647999d
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.createConnection(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.newConnection(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
at com.sun.proxy.$Proxy26.isAlive(Unknown Source)
at com.servoy.j2db.dataprocessing.ClientProxy.Zc(ClientProxy.java:164)
at com.servoy.j2db.dataprocessing.Zo.run(Zo.java:19)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.net.ConnectException: no multiplexer found for server with id=597ec4dc-3a47-4a5f-bc7d-785c4647999d
at com.sebster.tunnel.impl.hd.createSocket(hd.java:12)
at com.servoy.j2db.server.rmi.tunnel.WrappingCompressingRMIClientSocketFactory.createSocket(WrappingCompressingRMIClientSocketFactory.java:28)

Tnx in advance