.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "CONNECT" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" connect 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
connect \- connect a socket
.SH SYNOPSIS
.LP
\fB#include <sys/socket.h>
.br
.sp
int connect(int\fP \fIsocket\fP\fB, const struct sockaddr *\fP\fIaddress\fP\fB,
.br
\ \ \ \ \ \  socklen_t\fP \fIaddress_len\fP\fB);
.br
\fP
.SH DESCRIPTION
.LP
The \fIconnect\fP() function shall attempt to make a connection on
a socket. The function takes the following arguments:
.TP 7
\fIsocket\fP
Specifies the file descriptor associated with the socket.
.TP 7
\fIaddress\fP
Points to a \fBsockaddr\fP structure containing the peer address.
The length and format of the address depend on the address
family of the socket.
.TP 7
\fIaddress_len\fP
Specifies the length of the \fBsockaddr\fP structure pointed to by
the \fIaddress\fP argument.
.sp
.LP
If the socket has not already been bound to a local address, \fIconnect\fP()
shall bind it to an address which, unless the
socket's address family is AF_UNIX, is an unused local address.
.LP
If the initiating socket is not connection-mode, then \fIconnect\fP()
shall set the socket's peer address, and no connection is
made. For SOCK_DGRAM sockets, the peer address identifies where all
datagrams are sent on subsequent \fIsend\fP() functions, and limits
the remote sender for subsequent \fIrecv\fP() functions. If \fIaddress\fP
is a null address for the protocol, the socket's peer
address shall be reset.
.LP
If the initiating socket is connection-mode, then \fIconnect\fP()
shall attempt to establish a connection to the address
specified by the \fIaddress\fP argument. If the connection cannot
be established immediately and O_NONBLOCK is not set for the
file descriptor for the socket, \fIconnect\fP() shall block for up
to an unspecified timeout interval until the connection is
established. If the timeout interval expires before the connection
is established, \fIconnect\fP() shall fail and the connection
attempt shall be aborted. If \fIconnect\fP() is interrupted by a signal
that is caught while blocked waiting to establish a
connection, \fIconnect\fP() shall fail and set \fIerrno\fP to [EINTR],
but the connection request shall not be aborted, and the
connection shall be established asynchronously.
.LP
If the connection cannot be established immediately and O_NONBLOCK
is set for the file descriptor for the socket,
\fIconnect\fP() shall fail and set \fIerrno\fP to [EINPROGRESS], but
the connection request shall not be aborted, and the
connection shall be established asynchronously. Subsequent calls to
\fIconnect\fP() for the same socket, before the connection is
established, shall fail and set \fIerrno\fP to [EALREADY].
.LP
When the connection has been established asynchronously, \fIselect\fP()
and \fIpoll\fP() shall indicate that the file descriptor for the socket
is ready for writing.
.LP
The socket in use may require the process to have appropriate privileges
to use the \fIconnect\fP() function.
.SH RETURN VALUE
.LP
Upon successful completion, \fIconnect\fP() shall return 0; otherwise,
-1 shall be returned and \fIerrno\fP set to indicate
the error.
.SH ERRORS
.LP
The \fIconnect\fP() function shall fail if:
.TP 7
.B EADDRNOTAVAIL
The specified address is not available from the local machine.
.TP 7
.B EAFNOSUPPORT
The specified address is not a valid address for the address family
of the specified socket.
.TP 7
.B EALREADY
A connection request is already in progress for the specified socket.
.TP 7
.B EBADF
The \fIsocket\fP argument is not a valid file descriptor.
.TP 7
.B ECONNREFUSED
The target address was not listening for connections or refused the
connection request.
.TP 7
.B EINPROGRESS
O_NONBLOCK is set for the file descriptor for the socket and the connection
cannot be immediately established; the connection
shall be established asynchronously.
.TP 7
.B EINTR
The attempt to establish a connection was interrupted by delivery
of a signal that was caught; the connection shall be
established asynchronously.
.TP 7
.B EISCONN
The specified socket is connection-mode and is already connected.
.TP 7
.B ENETUNREACH
No route to the network is present.
.TP 7
.B ENOTSOCK
The \fIsocket\fP argument does not refer to a socket.
.TP 7
.B EPROTOTYPE
The specified address has a different type than the socket bound to
the specified peer address.
.TP 7
.B ETIMEDOUT
The attempt to connect timed out before a connection was made.
.sp
.LP
If the address family of the socket is AF_UNIX, then \fIconnect\fP()
shall fail if:
.TP 7
.B EIO
An I/O error occurred while reading from or writing to the file system.
.TP 7
.B ELOOP
A loop exists in symbolic links encountered during resolution of the
pathname in \fIaddress\fP.
.TP 7
.B ENAMETOOLONG
A component of a pathname exceeded {NAME_MAX} characters, or an entire
pathname exceeded {PATH_MAX} characters.
.TP 7
.B ENOENT
A component of the pathname does not name an existing file or the
pathname is an empty string.
.TP 7
.B ENOTDIR
A component of the path prefix of the pathname in \fIaddress\fP is
not a directory.
.sp
.LP
The \fIconnect\fP() function may fail if:
.TP 7
.B EACCES
Search permission is denied for a component of the path prefix; or
write access to the named socket is denied.
.TP 7
.B EADDRINUSE
Attempt to establish a connection that uses addresses that are already
in use.
.TP 7
.B ECONNRESET
Remote host reset the connection request.
.TP 7
.B EHOSTUNREACH
The destination host cannot be reached (probably because the host
is down or a remote router cannot reach it).
.TP 7
.B EINVAL
The \fIaddress_len\fP argument is not a valid length for the address
family; or invalid address family in the \fBsockaddr\fP
structure.
.TP 7
.B ELOOP
More than {SYMLOOP_MAX} symbolic links were encountered during resolution
of the pathname in \fIaddress\fP.
.TP 7
.B ENAMETOOLONG
Pathname resolution of a symbolic link produced an intermediate result
whose length exceeds {PATH_MAX}.
.TP 7
.B ENETDOWN
The local network interface used to reach the destination is down.
.TP 7
.B ENOBUFS
No buffer space is available.
.TP 7
.B EOPNOTSUPP
The socket is listening and cannot be connected.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
If \fIconnect\fP() fails, the state of the socket is unspecified.
Conforming applications should close the file descriptor and
create a new socket before attempting to reconnect.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIaccept\fP(), \fIbind\fP(), \fIclose\fP(), \fIgetsockname\fP(),
\fIpoll\fP(), \fIselect\fP(), \fIsend\fP(), \fIshutdown\fP(),
\fIsocket\fP(), the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
\fI<sys/socket.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .