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I did set my kern.ipc.somaxconn kernel parameter to tweak the maximum backlog TCP size for incoming connections on my server. I'm now looking to read the current amount of request pending in this backlog.

I thought for a moment it was the number of connection in the state 'ESTABLISED' in the ouput of netstat, but I understood that requests being processed by the application could also be in this state.

Is there a file I have to read in the /proc/ filesystem, is it an option of netstat that I missed?

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If I understand the question correctly, I believe you're referring to the Recv-Q and Send-Q numbers from netstat.

If these numbers are not near zero, there is a high probability that there is either something going wrong with hardware, or that you are saturating your link.

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To clarify, Recv-Q: "The count of bytes not copied by the user program connected to this socket." and Send-Q: "The count of bytes not acknowledged by the remote host." (from the linux manual) –  rakslice Dec 13 '11 at 20:41

TCP connection's data are 1st received into a buffer which lies in kernelspace. In that case Recv-Q is non-zero. And then if process calls read are copied into userpace. If not(the app is saturated), they will remain in the kernel buffer.

PS: are you using Linux or FreeBSD?

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