The jboss clent library you need to include is... jboss-client.jar !
It is found in the <JBOSS_DIST>/client directory. (and is under 100KB)
I am not sure what other jars you might need, it doesn't seem to specify anywhere in the manual (unless I missed that page ?), but normally the jars you need for jboss clients are in this directory.
Thanx for your prompt reply!
It seems that jboss-client.jar is not enough, jbosssx-clien.jar is also necessary.
With these two jars all is fine. Their total size is some 120 KB.