[Mono-list] Native UDP socket close problem when calling C/C++ shared lib from C#/Mono

[edwin]

Hello,

I have searched this forum and the web using Google to try to find the
answer to my issue but I failed. That is why I am posting here. Thank you in
advance for any help.


Problem:
-- Native UDP socket bind errors -- 
I have a native shared VOIP library that has been ported to Ubuntu Linux
10.04 from Windows. The shared native C/C++ library has a managed wrapper
that allows C#/Mono code to call into the native shared library. Everything
is working quite well…

However, when running the managed code C# test driver application I
developed to test/verify everything, I am experiencing UDP port bind errors.
I get the same UDP port bind errors when I run under the Monodevelop soft
debugger and from a terminal.

Basically in the native code shared library, a UDP SIP port is opened, then
used, and finally closed. When I want to use the SIP port again (by calling
into the native shared library) to open and bind to the SIP port, my native
code shared library cannot bind to the port and it then return its “cannot
bind to port” error indication.

Upon further investigation, I see that when the UDP port gets closed by the
native code, the UDP port is still shown to be in use by the system. If I
open the SIP UDP port and then close it, the socklist script available on
Ubuntu shows that the port (5092 in this case) has a pid and an fd of zero
and there is no process name. Here is the output from socklist after a
simple SIP port open and close for UDP port 5092:

type  port      inode     uid    pid   fd  name
tcp  34771      75589    1000  17093   50  monodevelop
tcp     22       4602       0      0    0  
tcp    631       7595       0      0    0  
tcp    445       4016       0      0    0  
tcp    139       4018       0      0    0  
tcp  34771      75590    1000  17093   53  monodevelop
tcp  56021      60469    1000  17093   42  monodevelop
tcp  45705      75333    1000  17093   51  monodevelop
tcp  44527          0       0      0    0  
tcp  57580      75653    1000  25002    3  mono
tcp  58243      59112    1000  17093   41  monodevelop
tcp  44841      67587    1000  17093   49  monodevelop
tcp  51347      61611    1000  17093   45  monodevelop
tcp  57297      65433    1000  17093   46  monodevelop
tcp  56398      58899    1000  17093   43  monodevelop
udp  55625      75721    1000  25002    5  mono
udp   5090      75738    1000  25002    6  mono
udp   5092      75760    1000      0    0 
udp   5353       3928     110      0    0  
udp  45942       3929     110      0    0  
udp    137       4655       0      0    0  
udp    137       4652       0      0    0  
udp    138       4656       0      0    0  
udp    138       4653       0      0    0  

Apparently the system still thinks the UDP socket is being used even though
it has been closed by the native code on behalf of the C#/Mono managed code
test application. Hmmm…. Stange... I see no native socket close errors being
reported.

One other item I would like to mention – When I execute this same managed
code and native shared library using CodeBlocks IDE (and the typical GNU
tool chain and gdb debugger) everything executes without issue. Hmmm…..

Any help would be very much appreciated. The mono project is very cool.


Thank you,

edwin




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