if you're referring to the xbms xns server, then the relax test client should be able to connect to an xbms server running on linux/bsd/osx.
if you're referring to an xbms:// url (which connects to a ccxstream server), then i dont think there are any test clients.
** edit: i just saw that ccxstream for win32 comes with ccxtest.exe if you need one for xbmsp protocol.
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