Incoming messages silently discarded #813
Description
For quite a long time I've been randomly losing incoming messages, which was very frustrating. Finally, today I was able to figure out what exactly is happening. Turns out that ChatSecure assumes that every stanza id is unique for a given buddy, and discards a message if it has already seen a message with a given id. XMPP, however, does not guarantee that every id is unique:
The optional 'id' attribute MAY be used by a sending entity for
internal tracking of stanzas that it sends and receives (especially
for tracking the request-response interaction inherent in the
semantics of IQ stanzas). It is OPTIONAL for the value of the 'id'
attribute to be unique globally, within a domain, or within a stream.
There are clients (e.g. @psi-im) that use sequential ids for stanzas. So, whenever such client is restarted, ChatSecure is not going to see any messages from it until the id exceeds the last seen.
I don't know what problem the id-based check for duplicates was meant to solve, but it seems that it breaks the standard and needs to be removed as soon as possible.