latency between the client and the server

hi all,

i had a problem with my flash builder 4.6 application that;

when i leave the application ABOUT 2 minutes idle, then trying to call the netconnection for example to get the chat history or send a message or invoke a function at the serverside, it suddenly says netconnection.connect.closed after trying to call the netconnection..

while these happening, i am watching fms admin console but the client doesnt drop and seems still connected.. even i close the browser, the client is still there in the fms admin console..(normally if i use nc.close() method the client drops immediatley in the fms admin console or when i close the browser the client drops..)

then still watching and after ABOUT 10 minutes, i see the client drops in the fms admin console finally but after 10 minutes..

i tried the same app in the "localhost", it works fine.. net connection never closes.. i waited so long time idle and then called the netconnection.. it worked very well..

but when i try to run my app on the server i had the problem above..

i tired flash media development server 3.5 and 4.0.3.. i had this problem on both of them, but i know it is not about the fms versions because i had no problem on the localhost so it is not about fms versions..

extra information: i am using flash media development server on my centos 5, 32bit server on digitalocean.. and the pepper flash player is DISABLED on the browser..

what is the reason of this problem ?? please help.. i am really sad about this problem cause i couldnt solve..

is it about tcp, http or something different ?