HP 3000 Manuals HP 3000 Manuals
LISTEN
C Interface
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:
[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