Originální popis anglicky:
listen - listen for connections on a socket
Návod, kniha: Linux Programmer's Manual
#include <sys/socket.h>
int listen(int s, int backlog);
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
listen, and then the connections are
accepted with
accept(2). The
listen call applies only to sockets
of type
SOCK_STREAM or
SOCK_SEQPACKET.
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 indication of
ECONNREFUSED or,
if the underlying protocol supports retransmission, the request may be ignored
so that retries succeed.
The behaviour of the
backlog parameter on TCP sockets changed with Linux
2.2. Now it specifies the queue length for
completely established
sockets waiting to be accepted, instead of the number of incomplete connection
requests. The maximum length of the queue for incomplete sockets can be set
using the
tcp_max_syn_backlog sysctl. When syncookies are enabled there
is no logical maximum length and this sysctl setting is ignored. See
tcp(7) for more information.
On success, zero is returned. On error, -1 is returned, and
errno is set
appropriately.
- EADDRINUSE
- Another socket is already listening on the same port.
- EBADF
- The argument s is not a valid descriptor.
- ENOTSOCK
- The argument s is not a socket.
- EOPNOTSUPP
- The socket is not of a type that supports the listen
operation.
Single Unix, 4.4BSD, POSIX 1003.1g draft. The
listen function call first
appeared in 4.2BSD.
If the socket is of type
AF_INET, and the
backlog argument is
greater than the constant
SOMAXCONN (128 in Linux 2.0 & 2.2), it is
silently truncated to
SOMAXCONN. Don't rely on this value in portable
applications since BSD (and some BSD-derived systems) limit the backlog to 5.
accept(2),
connect(2),
socket(2)
