Here is my mail posted in the developer mailing list describing the issue(s):
Hi xmlrpc-gurus!

I am trying to migrate my projects from xmlrpc 2.0 to xmlrpc 3.1. I need to migrate one of the clients and the server, so I am very interested, that this part of the documentation is true:

> If streaming mode is disabled, then the server will always behave like a standard XML-RPC server. Otherwise, the server will verify, whether the client sends a content-length header. If so, then the server assumes that
> the client is able to accept a missing content-length header in the response as well. Otherwise, the server will still disable streaming for this particular requests. In other words, traditional clients will still receive a traditional > response and one server can serve both data types.

Unfortunately during verification of this I encountered two problems:

1) client: I am using the sun classes on a linux system. It looks like that it doesn't actually matters if I set contentLengthOptional and enabledForExtensions to tue or false. The request _always_ contains a content-length header. I debugged it but couldn't find place, where this header is added. I found the place in the client where the configuration was correctly read out and where the client was skipping the part to add this header. But nevertheless my request contains a content-length header at the end (I am using wireshark to sniff the network traffic). In the case I set the two configurations to true, the content-length header is always the last header in the header section. Can it be, that java is adding the content-length header by itself? If this is the case then using the content-length header for detection if the server should answer in streaming mode or not is not working!

2) server: I actually can't find the part in the sources where the server is honoring the content-length header in the request. It looks like the server is acting in streaming mode if I set both options to true and is not acting in streaming-mode, if I set both options to false. At least that is wireshark telling me. Could you give me a pointer to the code part that is doing the magic as stated in the documentation?

I don't want to nit-pick, but not becoming incompatible is essential for my service. Within the enterprise of my customer a number of clients are not under my control and I am in deep shit if they stop working :)

Thanks for your time guys!