[jdev] does write new extension required to write server plugin?

[cw]

i came across smack extension http://www.igniterealtime.org/builds/smack/docs/latest/documentation/extensions/index.html  . it doesnt required to install new extension/plugin on server in order to use it.  May i know if i want to use new extension,  beside writing the extension using "smack client api" is there requirement to write extension/plugin and install on server ?