methods of communication

[tcyhunt]

No: HPFGUIDX 68764

I now know that I've been on this list too long -- I see large 
question marks looming over even the simplist of phrases.  In "The 
Lost Prophecy" (pg. 830, American Edition), Dumbledore says to 
Harry:  

"He [Snape], like you, attempted to contact Serius at once.  I should 
explain that members of the Order of the Phoenix have more reliable 
methods of communicating than the fire in Dolores Umbridge's office."

What does he mean by 'more reliable methods of communicating'?  And 
does this mean that the methods we know of (owls, floo powder, 
howlers, etc.) are UNreliable?

Any thoughts?

Tcy