connect(3sock)
connect --
initiate a connection on a socket
Synopsis
cc [options] file -lsocket -lnsl
#include <sys/types.h>
#include <sys/socket.h>
int connect(int socket, const struct sockaddr *address, size_t address_len);
Description
connect requests that a connection be made on a socket.
If the initiating socket is not connection-oriented, then
connect sets the socket's peer address but no connection is
made.
For SOCK_DGRAM sockets, the peer address identifies where all
datagrams are sent on subsequent
send(3sock)
calls, and limits the
remote sender for subsequent
recv(3sock)
calls.
If address is a null address for the protocol, the socket's peer
address will be reset.
If the initiating socket is connection-oriented, then connect
attempts to establish a connection to the address specified by
address.
If the connection cannot be established immediately and
O_NONBLOCK is not set for the file descriptor for the socket,
connect will block for up to an unspecified timeout
interval until the connection is established.
If the timeout interval expires before the connection is established,
connect will fail and the connection attempt will be aborted.
If connect is interrupted by a signal that is caught while
blocked waiting to connect, connect will fail and set
errno to EINTR, but the connection request will not be
aborted, and the connection will be established asynchronously.
If the connection cannot be established immediately and
O_NONBLOCK is set for the file descriptor for the socket,
connect will fail and set errno to EINPROGRESS, but
the connection request will not be aborted, and the connection will be
established asynchronously.
Subsequent calls to connect for the same socket, before the
connection is established, will fail and set errno to
EALREADY.
When the connection has been established asynchronously,
select(3C)
and
poll(2)
will indicate that the file
descriptor for the socket is ready for writing.
However, this is only possible if the socket STREAMS module
is the topmost module on the protocol stack with a write service
procedure.
This will be the normal case.
Files
/usr/lib/locale/locale/LC_MESSAGES/uxns1
Return values
If the connection or binding succeeds, then
0 is returned.
Otherwise a -1 is returned and a more specific error
code is stored in
errno.
Errors
The call fails if:
EADDRNOTAVAIL-
The specified address is not available from the local machine.
EAFNOSUPPORT-
Addresses in the specified address family cannot be used with this
socket.
EALREADY-
A connection request is already in progress for the specified socket.
EBADF-
socket
is not a valid descriptor.
ECONNREFUSED-
The attempt to connect was refused or the target address was not
listening for connections.
EINPROGRESS-
The socket is non-blocking and the connection cannot be completed
immediately; the connection will be established asynchronously.
EINTR-
The connection attempt was interrupted before
any data arrived by the delivery of a signal.
The connection will be established asynchronously.
EISCONN-
The socket is connection-oriented, and is already connected.
ENETUNREACH-
The network is not reachable from this host.
ENOTSOCK-
socket
does not refer to a socket.
EPROTOTYPE-
The file referred to by
address
is a socket of a type other than the socket bound to the specified
peer address.
ETIMEDOUT-
Connection establishment timed out without establishing a connection.
EADDRINUSE-
The address is already in use.
ECONNRESET-
The remote host reset the connection request.
EINVAL-
address_len
is not the size of a valid address for the specified address family,
or invalid address family in sockaddr structure.
ENAMETOOLONG-
Pathname resolution of a symbolic link produced an intermediate result
whose length exceeds PATH_MAX.
ENETDOWN-
The local interface used to reach the destination is down.
ENOBUFS-
No buffer space is available.
ENOSR-
There were insufficient
STREAMS
resources available to complete
the operation.
If the address family of the socket is AF_UNIX, connect will
fail if:
ENOTDIR-
A component of the path prefix of the pathname in
address
is not a directory.
ENAMETOOLONG-
A component of a pathname exceeded NAME_MAX characters or an
entire pathname exceeded
PATH_MAX.
EACCES-
Search permission is denied for a component of the path prefix
or write access to the named socket is denied.
EIO-
An I/O error occurred while reading from or writing to the file
system.
ELOOP-
Too many symbolic links were encountered in translating the pathname
in
address.
ENOENT-
A component of the pathname does not name an existing file or the
pathname is an empty string.
References
accept(3sock),
close(2),
getsockname(3sock),
socket(3sock)
RFC 2133
Notices
The behavior of non-blocking
connect for unix domain (AF_UNIX)
sockets is determined by the value of the ss_connafunixndelay
parameter set by
inconfig(1Mtcp).
The type of address structure passed to connect depends on the
address family.
UNIX® domain sockets (address family AF_UNIX) require a
socketaddr_un structure as defined in sys/un.h;
Internet domain IPv4 sockets (address family AF_INET)
require a sockaddr_in structure as defined in
netinet/in.h; Internet domain IPv6 sockets (address family
AF_INET6)
require a sockaddr_in6 structure as defined in
netinet/in.h.
Other address families may require other structures.
Use the structure appropriate to the address family; cast the
structure address to a generic struct sockaddr * in the call to
connect
and pass the size of the structure in the length argument.
If connect fails, the state of the socket is unspecified.
Portable applications should close the file descriptor and create a
new socket before attempting to reconnect.
In UnixWare 7 the sockaddr structure has been modified
to support variable length sockets. The net result of this modification
is that the family
member has been shortened to 8 bits and a
new 8-bit member inserted before it called len
. For more
information on the new sockaddr structures, see:
unix(7sock)
and
inet(7tcp).
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004