[Mono-dev] Need help with Sockets

[Bernhard Herzog]

Thanks, that's interesting stuff.

My application is a chat server, so I really need to know sooner than 2 
hours if the client is dead. On the other hand I have a web server and don't 
want to introduce unnecessary traffic there. What is the right way to handle 
this, right now I am just sending out some data - do I need to send it back 
on the client (which would make things very complicated because I would need 
timeouts) or is it sufficient to just send it out from the server to get an 
exception? Or is there a problem in Mono, because with .Net it works 
flawlessly?

Thanks again
Bernhard

----- Original Message ----- 
Good day.

You can try to tune keepalive TCP parameters. These parameters can be
setted via /proc file system. You can write values directly to
pseudo-files, set them with sysctl utility, or add them to
/etc/sysctl.conf. See man page for  sysctl for details.

Keepalive parameters that could be useful for your case are these:

net.ipv4.tcp_keepalive_intvl
net.ipv4.tcp_keepalive_probes
net.ipv4.tcp_keepalive_time

For Suse Linux 9.2 they are setted as optimal for web-server:
net.ipv4.tcp_keepalive_intvl = 75 - how long to wait between to probes
for client alive (seconds)
net.ipv4.tcp_keepalive_probes = 9 - how many probes to send before idle
TCP connection force termination (units)
net.ipv4.tcp_keepalive_time = 7200 - how long to wait on idle connection
before check it for client alive (seconds)

BTW, same for Windows defaults are: 1/5/7200.

IMHO, you should change last parameter (2 hours) for something less. How
long is depend on how long your connections should be keeped idle and
how costly for you to open new connection.


-----Original Message-----
Hi!

I have a Socket Server and Clients (see attached files). When
disconnecting the clients the server does not receive exceptions on some
of the clients. I have a cleanup routine that periodically checks the
clients by sending some empty data. But this does not work for some of
the clients (232 out of 360 connections are still "alive" on the server
after closing the clients).

Actually I created this client and server programs to test this
particular
bug:
http://bugzilla.ximian.com/show_bug.cgi?id=75812

But this problem does not show in my simplified test programs, but it
does not work correctly nevertheless. The programs does work on MS .Net
(BTW: The socket client program does not work on Mono for Windows, maybe
this is the same problem that the MySql Connector is having on Windows
in 1.1.8.3 -> but this is a different bug).

Maybe someone can have a look, I would really appreciate that. I have
not posted any bug reports yet (except for the one above). This is
really a major issue for me (kind of a show stopper). Maybe I am doing
something very wrong, I don't know. I am using 1.1.8.3 on Suse Linux
9.2.

Thank you
Bernhard