HPUX connect[2]
connect(2) connect(2)
NAME
connect - initiate a connection on a socket
SYNOPSIS
#include <sys/socket.h>
AF_INET only:
#include <netinet/in.h>
AF_UNIX only:
#include <sys/un.h>
AF_CCITT only:
#include <x25/x25addrstr.h>
int connect(int s, const void *addr, int addrlen);
DESCRIPTION
connect() initiates a connection on a socket.
The parameter s is a socket descriptor. addr is a pointer to a socket
address structure containing the address of a remote socket to which a
connection is to be established. addrlen is the size of this address
structure. Since the size of the socket address structure varies
among socket address families, the correct socket address structure
should be used with each address family (for example, struct
sockaddr_in for AF_INET, and struct sockaddr_un for AF_UNIX).
Typically, the sizeof() function is used to pass this value (for
example, sizeof(struct sockaddr_in)).
If the socket is of type SOCK_DGRAM, connect() specifies the peer
address to which messages are to be sent, and the call returns
immediately. Furthermore, this socket can only receive messages sent
from this address.
If the socket is of type SOCK_STREAM, connect() attempts to contact
the remote host in order to make a connection between the remote
socket (peer) and the local socket specified by s. The call normally
blocks until the connection completes. If non-blocking mode has been
enabled using the O_NONBLOCK or O_NDELAY fcntl() flags or the FIOSNBIO
ioctl() request and the connection cannot be completed immediately,
connect() returns an error as described below. In these cases,
select() can be used on this socket to determine when the connection
has completed by selecting it for writing.
O_NONBLOCK and O_NDELAY are defined in <sys/fcntl.h> and explained in
fcntl(2), fcntl(5), and socket(7). FIOSNBIO is defined in
<sys/ioctl.h> and explained in ioctl(2), ioctl(5), and socket(7).
If s is a SOCK_STREAM socket that is bound to the same local address
as another SOCK_STREAM socket, connect() returns EADDRINUSE if addr is
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connect(2) connect(2)
the same as the peer address of that other socket. This situation can
only happen if the SO_REUSEADDR option has been set on an AF_INET
socket (see getsockopt(2)).
If the AF_INET socket does not already have a local name bound to it
(see bind(2)), connect() also binds the socket to a local address
chosen by the system.
Generally, stream sockets may successfully connect only once; datagram
sockets may use connect() multiple times to change the peer address.
For datagram sockets, a side effect of attempting to connect to some
invalid address (see DIAGNOSTICS below) is that the peer address is no
longer maintained by the system. An example of an invalid address for
a datagram socket is addrlen set to 0 and addr set to any value.
AF_CCITT only:
Use the x25addrstr struct for the address structure. The caller must
know the X.121 address of the DTE to which the connection is to be
established, including any sub-addresses or protocol-IDs that may be
needed. Refer to af_ccitt(7F) for a detailed description of the
x25addrstr address structure. If address-matching by protocol-ID,
specify the protocol-ID with the X25_WR_USER_DATA ioctl() call before
issuing the connect() call. The X25_WR_USER_DATA ioctl() call is
described in socketx25(7).
DEPENDENCIES
AF_CCITT:
The SO_REUSEADDR option to setsockopt() is not supported for sockets
in the AF_CCITT address family.
RETURN VALUE
Upon successful completion, connect() returns 0; otherwise it returns
-1 and sets errno to indicate the error.
DIAGNOSTICS
connect() fails if any of the following conditions are encountered:
[EBADF] s is not a valid file descriptor.
[ENOTSOCK] s is a file descriptor for a file, not a
socket.
[EADDRNOTAVAIL] The specified address is not available
on this machine, or the socket is a TCP
or UDP socket and the zero port number
is specified.
For datagram sockets, the peer address
is no longer maintained by the system.
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[EAFNOSUPPORT] Addresses in the specified address
family cannot be used with this socket.
For datagram sockets, the peer address
is no longer maintained by the system.
[EALREADY] Non-blocking I/O is enabled using
O_NONBLOCK, O_NDELAY, or FIOSNBIO, and a
previous connection attempt has not yet
completed.
[EISCONN] The socket is already connected.
[EINVAL] The socket has already been shut down,
or has a listen() active on it; addrlen
is a bad value; an attempt was made to
connect() an AF_UNIX socket to an NFS
-mounted (remote) name; the X.121
address length is zero, negative, or
greater than fifteen digits.
For datagram sockets, if addrlen is a
bad value, the peer address is no longer
maintained by the system.
[ETIMEDOUT] Connection establishment timed out
without establishing a connection.
backlog may be full (see listen(2)).
[ECONNREFUSED] The attempt to connect was forcefully
rejected.
[ENETUNREACH] The network is not reachable from this
host.
For AF_CCITT only: X.25 Level 2 is down.
The X.25 link is not working: wires
might be broken, or connections are
loose on the interface hoods at the
modem, or the modem failed, or noise
interfered with the line for an
extremely long period of time.
[EADDRINUSE] The address is already in use.
For datagram sockets, the peer address
is no longer maintained by the system.
[EFAULT] addr is not a valid pointer.
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[EINPROGRESS] Non-blocking I/O is enabled using
O_NONBLOCK, O_NDELAY, or FIOSNBIO, and
the connection cannot be completed
immediately. This is not a failure.
Make the connect() call again a few
seconds later. Alternatively, wait for
completion by calling select(),
selecting for write.
[ENODEV] The x25ifname field refers to a non-
existent interface.
[ENOSPC] All available virtual circuits are in
use.
[ENETDOWN] The X.25 interface specified in the addr
struct was found or but was not in the
initialized state. x25ifname field name
is an interface which has been shut down
or never initialized or suffered a power
failure which erased its state
information.
[ENOBUFS] No buffer space is available. The
connect() has failed.
[EINTR] The connect was interrupted by delivery
of a signal before the connect sequence
was complete. The building of the
connection still takes place, even
though the user is not blocked on the
connect() call.
[EOPNOTSUPP] A connect() attempt was made on a socket
type which does not support this call.
Under X.25 an attempt was made to issue
a connect() call on a listen() socket.
AUTHOR
connect() was developed by the University of California, Berkeley.
SEE ALSO
accept(2), select(2), socket(2), getsockname(2), socket(7),
socketx25(7), af_ccitt(7F).
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