Re: Re: [RFC PATCH 08/11] trace-cmd: Apply the trace-msg protocolfor communication between a server and clients

[Yoshihiro YUNOMAE]

(2013/08/27 22:05), Steven Rostedt wrote:
> On Tue, 27 Aug 2013 19:23:24 +0900
> Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx> wrote:
>
> > OK, let me check that. Even if the old server will receive "V2", the
> > server will send port numbers instead of "V2" due to the old protocol.
> > In that time, the new client will disconnect from the old server and
> > the restarts with the old protocol. Is it OK?
>
> Yep, that's exactly what I meant ;-)

I tried to implement the feature, but I found that sending just "V2"
from the new client is inappropriate. This is because the old server
doesn't respond to the client before receiving cpu numbers, page size,
and options. So, when the new client sends the first message, it should
send "V2\0<MAGIC_NUMBER>\00\0", I think. If so, the old server will
understand the message as cpus=0, pagesize=<MAGIC_NUMBER>, options=0,
and then it will send port numbers(actually \0). Note if <MAGIC_NUMBER>
is zero, the old server will die.

Can I implement the first message of the new client as
"V2\0<MAGIC_NUMBER>\00\0"?

Thanks,
Yoshihiro YUNOMAE

--
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@xxxxxxxxxxx


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