|
|
|
C Interface
int listen (s, backlog)
int s, backlog;
Description
To accept connections, a socket is first created with socket, a queue
for incoming connections is specified with listen, and then
connections are accepted with accept. The listen call
applies only to unconnected sockets of type SOCK_STREAM. Note that
you cannot call listen after accept has been called. If the
socket has not been bound to a local port before the listen is
invoked, the system automatically binds a local port for the socket to listen
on.
The listen queue is established for the socket specified by the
s parameter, which is a socket descriptor.
The backlog parameter defines the maximum allowable length of
the queue for pending connections. If a connection request arrives when the
queue is full, the client receives an ETIMEDOUT error.
The backlog parameter is limited (silently) to be in the range
of 1 to 128. If you specify any other value, the system automatically assigns
the closest value within range.
Return Value
If the call is successful, 0 is returned. If the call fails, a -1 is returned,
and an error code is stored in errno.
Errors
The following errors are returned by listen:
| Error Code |
Description |
| [EBADF] |
The argument s is not a valid descriptor. |
| [EDESTADDRREQ] |
No bind address was established. |
| [ENOTSOCK]
| The argument s is not a socket. |
| [EOPNOTSUPP] |
The socket is not of a type that supports the listen
operation. |
| [ENOBUFS] |
Series 300 only: No buffer space is available. The listen call
cannot be started at this time. |
| [EINVAL] |
The socket has been shut down or is already connected. |
MPE/iX Specific
The backlog limit on MPE/iX is 128 as opposed to the backlog limit of 20 on
HP-UX. When an HP-UX socket has performed a listen, the incoming
connection requests are completed as they are received (up to the
backlog limit). When using MPE/iX, connections are completed
by the call to accept.
Author
UCB (University of California at Berkeley)
See Also
accept,
connect,
socket
|
