def FeaturesHandler(self,conn,feats):
        """ Used to determine if server supports SASL auth. Used internally. """
        if not feats.getTag('mechanisms',namespace=NS_SASL):
            self.startsasl='not-supported'
            self.DEBUG('SASL not supported by server','error')
            return
        mecs=[]
        for mec in feats.getTag('mechanisms',namespace=NS_SASL).getTags('mechanism'):
            mecs.append(mec.getData())
        self._owner.RegisterHandler('challenge',self.SASLHandler,xmlns=NS_SASL)
        self._owner.RegisterHandler('failure',self.SASLHandler,xmlns=NS_SASL)
        self._owner.RegisterHandler('success',self.SASLHandler,xmlns=NS_SASL)
        if "ANONYMOUS" in mecs and self.username == None:
            node=Node('auth',attrs={'xmlns':NS_SASL,'mechanism':'ANONYMOUS'})
        elif "DIGEST-MD5" in mecs:
            node=Node('auth',attrs={'xmlns':NS_SASL,'mechanism':'DIGEST-MD5'})
        elif "PLAIN" in mecs:
            sasl_data='%s\x00%s\x00%s'%(self.username+'@'+self._owner.Server,self.username,self.password)
            node=Node('auth',attrs={'xmlns':NS_SASL,'mechanism':'PLAIN'},payload=[base64.encodestring(sasl_data).replace('\r','').replace('\n','')])
        else:
            self.startsasl='failure'
            self.DEBUG('I can only use DIGEST-MD5 and PLAIN mecanisms.','error')
            return
        self.startsasl='in-process'
        self._owner.send(node.__str__())
        raise NodeProcessed
 Used to determine if server supports SASL auth. Used internally. 
chrome-cordova/gcmServer/xmpp/auth.py