backlog value in listen system call

I have a doubt regarding the backlog value in listen system call. From man page of listen system call.

If the backlog argument is greater than the value in /proc/sys/net/core/somaxconn, then it is silently truncated to that value; the default value in this file is 128.

It means my server can accept only <128 connections at once. What if I want to accept more connection >128 ?? Can I simply set the value to the possible maximum number so that I can access more numbe开发者_如何学Gor of connection ??

That number is only the size of the connection queue, where new connections wait for somebody to accept them. As soon as your application calls accept(), a waiting connection is removed from that queue. So, you can definitely handle more than 128 simultaneous connections because they usually only spend a short time in the queue.

Yes. Use a command such as

$ echo 1000 >/proc/sys/net/core/somaxconn

To set the limit higher. See, for instance, this page for more tuning tips.

The backlog value is not the number of maximum connections, it's the number of outstanding connections, i.e connections which you havn't accept():ed.