listen for connections on a
To accept connections, a socket is first created with
socket(2), a willingness to accept incoming connections and a queue
limit for incoming connections are specified with
and then the connections are accepted with
listen() call applies only to
sockets of type
The backlog parameter defines the maximum
length the queue of pending connections may grow to. If a connection request
arrives with the queue full the client may receive an error with an
ECONNREFUSED, or, if the underlying
protocol supports retransmission, the request may be ignored so that retries
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
listen() will fail if:
- The argument s is not a valid descriptor.
- The argument s is not a socket.
- The socket is not of a type that supports the operation
- The socket is already connected.
accept(2), connect(2), socket(2), sysctl(8)
listen() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”).
listen() system call first appeared in
The backlog is currently limited (silently) to the value of the kern.somaxconn sysctl, which defaults to 128.