LISTEN(2) | System Calls Manual | LISTEN(2) |
listen
— listen
for connections on a socket
#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
may succeed.
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:
EBADF
]ENOTSOCK
]EOPNOTSUPP
]listen
().EINVAL
]The listen
() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”).
The listen
() system call first appeared in
4.1cBSD.
The backlog is currently limited (silently) to the value of the kern.somaxconn sysctl, which defaults to 128.
September 10, 2015 | OpenBSD-6.9 |