NAME
listen —
listen for connections on a
socket
SYNOPSIS
#include
<sys/socket.h>
int
listen(int socket,
int backlog);
DESCRIPTION
Creation of socket-based connections requires several operations.
First, a socket is created with
socket(2).
Next, a willingness to accept incoming connections and a queue limit for
incoming connections are specified with
listen().
Finally, the connections are accepted with
accept(2).
The listen() call applies only to sockets of type
SOCK_STREAM.
The backlog parameter defines the maximum
length for the queue of pending connections. If a connection request arrives
with the queue full, the client may receive an error with an indication of
ECONNREFUSED. Alternatively, if the underlying
protocol supports retransmission, the request may be ignored so that retries
may succeed.
RETURN VALUES
The listen() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate the
error.
ERRORS
listen() will fail if:
- [
EACCES] - The current process has insufficient privileges.
- [
EBADF] - The argument socket is not a valid file descriptor.
- [
EDESTADDRREQ] - The socket is not bound to a local address and the protocol does not support listening on an unbound socket.
- [
EINVAL] - socket is already connected.
- [
ENOTSOCK] - The argument socket does not reference a socket.
- [
EOPNOTSUPP] - The socket is not of a type that supports the operation
listen().
SEE ALSO
BUGS
The backlog is currently limited (silently) to 128.
HISTORY
The listen() function call appeared in
4.2BSD.