resource identifier
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... session, or there may already be an active resource
associated with a resource identifier of the same name.
If the server encounters an internal condition that prevents it from
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... connection so that the newly-requested session has an opportunity to
negotiate a non-conflicting resource identifier before sending
another request for session establishment.
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... The examples in this section illustrate the presence-related
protocols described above. The user is romeo@example.net, he has an
available resource whose resource identifier is "orchard", and he has
the following individuals in his roster:
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... to the user's full JID, the server SHOULD remove the resource
identifier). If the contact is served by a different host than
the user, the user's server MUST route ...