listen(2)listen(2)NAMElisten - Listen for socket connections and limits the backlog of incom‐
ing connections
SYNOPSIS
#include <sys/socket.h>
int listen(
int socket,
int backlog );
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
listen(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Specifies the unique name for the socket. Specifies the maximum number
of outstanding connection requests.
DESCRIPTION
The listen() function identifies the socket that receives the connec‐
tions, 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 spec‐
ify is indicated by the somaxconn kernel attribute in the socket sub‐
system. 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 privi‐
leges to use the listen() function.
RETURN VALUES
Upon successful completion, the listen() function returns a value of 0
(zero). Otherwise, a value of -1 is returned and errno is set to indi‐
cate the error.
ERRORS
If the listen() function fails, errno may be set to one of the follow‐
ing values: The requested address is protected and the current process
does not have permission to access it. 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. The socket is already
connected; or the socket is shut down. Insufficient resources are
available in the system to complete the call. The socket parameter
refers to a file, not a socket. The referenced socket is not a type
that supports the listen() function.
SEE ALSO
Functions: accept(2), connect(2), socket(2)
Standards: standards(5)
Network Programmer's Guide
listen(2)