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<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'>Dear Robert, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'>Thank you for your
answer. I was trying to run several buffers in the same process, but running
them in different processes as you describe it seems to be very easier.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'>The modifications I did
to close the buffer cleanly make possible to run a new buffer after closing one,
in the same process. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'>Maybe it is not necessary
if buffers are created in different processes, but they are few modifications
and I find it is still convenient, so I submit it.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'>Best regards<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'>Amélie<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-GB
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-GB
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>De :</span></font></b><font
size=2 face=Tahoma><span lang=EN-GB style='font-size:10.0pt;font-family:Tahoma'>
Robert Oostenveld [mailto:r.oostenveld@donders.ru.nl] <br>
<b><span style='font-weight:bold'>Envoyé :</span></b> lundi 6 juin 2011
21:19<br>
<b><span style='font-weight:bold'>À :</span></b> Email disc</span></font><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>ussion
list for the FieldTrip project<br>
<b><span style='font-weight:bold'>Cc :</span></b> <st1:PersonName w:st="on">SERPOLLET
Amélie 228173</st1:PersonName><br>
<b><span style='font-weight:bold'>Objet :</span></b> Re: [FieldTrip]
questions about realtime buffer</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Dear Amelie<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<blockquote style='margin-top:5.0pt;margin-bottom:5.0pt' type=cite><span
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I’m implementing a realtime buffer in C++
pretty much like in “demo_combined” : my application creates a
buffer server and an acquisition client.<u1:p></u1:p></span></font><o:p></o:p></p>
</div>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I encountered a first problem when trying to close
the buffer server cleanly, but with some small changes in tcpsocket.c and
tcpserver.c, I think I solved the problem.<u1:p></u1:p></span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>If these modifications can be useful for other users
and do not create other problems, I will share them.<u1:p></u1:p></span></font><o:p></o:p></p>
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</blockquote>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'></span>If you have changes that don't break the ANSI-C compilation then
I am certainly happy to include them in our version. Please go to <a
href="http://bugzilla.fcdonders.nl">http://bugzilla.fcdonders.nl</a> and submit
a bug/request in which you attach the updated files.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I encounter now a new problem : what if there are
several acquisition clients ?<u1:p></u1:p></span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I tried to create several couples
“buffer-server + acquisition client” in different threads in my
application, but it does not work at all, because of global variables (I
suppose).</span></font><o:p></o:p></p>
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</blockquote>
</span>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>It seems that one buffer server can not manage
several acquisition clients, but I’m not sure of this point.<u1:p></u1:p></span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Did anyone encounter this problem (or solve it) ?<u1:p></u1:p></span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Or do anyone have an idea ?</span></font><o:p></o:p></p>
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</blockquote>
</span>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>You are right about the global variables. The buffer is implemented
using multithreading and to ensure that incoming data (Write) does not
interfere with outgoing (read) data a mutex (<a
href="http://en.wikipedia.org/wiki/Mutual_exclusion">http://en.wikipedia.org/wiki/Mutual_exclusion</a>)
is set. That mutex is shared throughout the code so that all pieces of code
are aware of when they are allowed to change the buffer content.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Having multiple buffers would require multiple mutexes and multiple
(separately identifyable) memory segments for the actual data. That would
require a lot of changes to the code.<o:p></o:p></span></font></p>
</div>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>You can run multiple buffers on the same computer, but you would have
to start them separately and they would have to have different TCP ports. The
application you are writing could write different aspects to the different TCP
ports. You can use fieldtrip/realtime/general/buffer.exe, which in fact is a
compiled version of fieldtrip/realtime/buffer/test/demo_buffer. Note that you
would use it as<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>buffer.exe localhost 2340<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>buffer.exe localhost 2341<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>buffer.exe localhost 2342<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>buffer.exe localhost 2343<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>to start 4 buffers on ports 2340-2343. The "localhost"
argument is not used, but still appears to be required according to the
demo_buffer.c source code. Of course it is cumbersome to have to start the 4
seperate processes on top of your own application. On unix-like computers you
should be able to write a single application that at the beginning forks into a
parent and child, where the parent continues as your application and where the
child (which is then a separate process) can start the buffer. You can fork
multiple times, to have multiple buffers (one per child). <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>best<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Robert<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
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