listen - Listens for socket connections and limits the backlog of incoming
int listen (
int backlog );
Interfaces documented on this reference page conform to industry standards
Refer to the standards(5) reference page for more information about indus-
try standards and associated tags.
socket Specifies the unique name for the socket.
backlog Specifies the maximum number of outstanding connection requests.
The listen() function identifies the socket that receives the connections,
marks the socket as accepting connections, and limits the number (backlog)
of outstanding connection requests in the system queue.
The maximum queue length (backlog) that the listen() function can specify
is indicated by the somaxconn kernel attribute in the socket subsystem.
Use the sysconfig -q socket somaxconn to obtain this value from the kernel.
See sys_attrs_socket(5) for more information.
The socket in use may require that the process have appropriate privileges
to use the listen() function.
Upon successful completion, the listen() function returns a value of 0
(zero). Otherwise, a value of -1 is returned and errno is set to indicate
If the listen() function fails, errno may be set to one of the following
[EACCES] The requested address is protected and the current process does
not have permission to access it.
[EBADF] The socket parameter is not valid.
The socket is not bound to a local address, and the protocol does
not support listening on an unbound socket.
[EINVAL] The socket is already connected; or the socket is shut down.
[ENOBUFS] Insufficient resources are available in the system to complete
The socket parameter refers to a file, not a socket.
The referenced socket is not a type that supports the listen()
Functions: accept(2), connect(2), socket(2)