Hi Werner,
re: "Each call to this bean starts a new WorkerThread on the server with a new TCP/IP-Port."
The server has an upper limit on the number of worker threads that can be created, which can be modified by setting the parameter "maxPoolSize", so you might be on the right track. If a client connects to the server and (1) all existing worker threads are in use, and (2) the number of worker threads has reached the upper limit, the server will wait for a worker thread to be returned to the pool. But the stack trace in your first comment shows that the worker thread has alread been created, so that doesn't seem to fit your hypothesis.
re: "This will throw an InvocationTargetException and SocketTimeout Exception on the server, because he can not open his prefered port."
I'm not sure what you mean by "prefered port".
re: "Is there any possibility to set the range for workerthread-ports in a higher direction?"
No, the sockets used by the worker threads are created by ServerSocket.accept().