- Case "chat with": The first messages do not lost
- Case "add contact": when 2 users are friends already. when two users login simultaneously, UserA sends messages to userB, but userB does not receive those ones. Until userB sends another messages back to UserA, then both of them can see those messages.
Why so? What do I thing to fix this error?

The example apps were designed to illustrate things in the book, but they may have weird edge cases.

Please post some traffic logs and I can try to debug what's going on.