https://developers.facebook.com/docs/chat
On April 30, 2014, we announced the deprecation of the XMPP Chat API as
part of the release of Platform API v2.0.
After April 30th, 2015 apps will no longer be able to access the service
or API. This includes both access to chat.facebook.com and the
xmpp_login permission.
We recommend people access Facebook Messages on the desktop via
Facebook.com or Messenger.com.
剛剛搜尋了一下發現沒人問過這事情，所以分享一下，
Facebook 即日起已經關閉了 XMPP 協定使用的 API，
換句話說，以後就不能再用 Pidgin 等第三方軟體來登入 Facebook Messenger 了
以上。