Menu
How should I determine what to use for a listening socket's backlog parameter? Is it a problem to simply specify a very large number?
853
The backlog has an effect on the maximum rate at which a server can accept new TCP connections on a socket. The rate is a function of both the backlog value and the time that connections stay on the queue of partially open connections.
The listen() call indicates a readiness to accept client connection requests. It transforms an active socket into a passive socket. Once called, socket can never be used as an active socket to initiate connection requests. Calling listen() is the third of four steps that a server performs to accept a connection.
The listen function converts an unconnected socket into a passive socket, indicating that the kernel should accept incoming connection requests directed to this socket. The second argument to this function specifies the maximum number of connections the kernel should queue for this socket.
SOMAXCONN defines the maximum number you're allowed to pass to listen() which is 128 on my system.
There's a very long answer to this in the Winsock Programmer's FAQ. It details the standard setting, and the dynamic backlog feature added in a hotfix to NT 4.0.
184
I second using SOMAXCONN, unless you have a specific reason to use a short queue.
Keep in mind that if there is no room in the queue for a new connection, no RST will be sent, allowing the client to automatically continue trying to connect by retransmitting SYN.
Also, the backlog argument can have different meanings in different socket implementations.
32
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
