process of instant message:

A and B:
A open client, log in the account , connect to the server
A sends connection information to server including IP address, port number of current using computer.

server:
create temporary file containint connection information for you and a list of contact of you.
check if any of contact are online. if finds, server send the connection information of that contacts to you.
server also send your connection information to that contacts.

A:
when you get the connection information of the contacts, the status of that contacts change to "online"
click the contact to begin end to end communication
enter message and hit enter
data will directly transfer to that contact, don't go via server.
all the message is stored in each computer

A:
close client,
client send message to server to terminate.
server sends message to all contact who is online, you are off-line.
server remove the temporary connection file

this is the messages between my and me

I'm scared when I open tim in the afternoon, I think I get wrong the time, and miss the appointment. but my friends said he didn't get it wrong, what he saw the same to me.
so I wonder why the messages vary from its orignal one?
doesn't he history message store locally or in the server? why the server collects the wrong order of messages ?