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.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
.\" Portions extracted from /usr/include/sys/socket.h, which does not have
.\" any authorship information in it. It is probably available under the GPL.
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.\" Other portions are from the 6.9 (Berkeley) 3/10/91 man page:
.\" Copyright (c) 1983 The Regents of the University of California.
.\" All rights reserved.
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.\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1998, 1999 by Andi Kleen
-.\" Modified 2004-06-23 by Michael Kerrisk <mtk-manpages@gmx.net>
+.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
-.TH CONNECT 2 2004-06-23 "Linux 2.6.7" "Linux Programmer's Manual"
+.TH CONNECT 2 2008-12-03 "Linux" "Linux Programmer's Manual"
.SH NAME
connect \- initiate a connection on a socket
.SH SYNOPSIS
-.B #include <sys/types.h>
+.nf
+.BR "#include <sys/types.h>" " /* See NOTES */"
.br
.B #include <sys/socket.h>
.sp
-.BI "int connect(int " sockfd ", const struct sockaddr *" serv_addr ,
-.BI "socklen_t " addrlen );
+.BI "int connect(int " sockfd ", const struct sockaddr *" addr ,
+.BI " socklen_t " addrlen );
+.fi
.SH DESCRIPTION
The
.BR connect ()
system call connects the socket referred to by the file descriptor
.I sockfd
to the address specified by
-.IR serv_addr .
+.IR addr .
The
-.IR addrlen
+.I addrlen
argument specifies the size of
-.IR serv_addr .
+.IR addr .
The format of the address in
-.I serv_addr
+.I addr
is determined by the address space of the socket
.IR sockfd ;
see
is of type
.B SOCK_DGRAM
then
-.I serv_addr
+.I addr
is the address to which datagrams are sent by default, and the only
-address from which datagrams are received. If the socket is of type
+address from which datagrams are received.
+If the socket is of type
.B SOCK_STREAM
or
.BR SOCK_SEQPACKET ,
this call attempts to make a connection to the socket that is bound
to the address specified by
-.IR serv_addr .
+.IR addr .
.PP
Generally, connection-based protocol sockets may successfully
.BR connect ()
only once; connectionless protocol sockets may use
.BR connect ()
-multiple times to change their association. Connectionless sockets may
-dissolve the association by connecting to an address with the
+multiple times to change their association.
+Connectionless sockets may
+dissolve the association by connecting to an address with the
.I sa_family
member of
-.B sockaddr
-set to
-.BR AF_UNSPEC .
-.SH "RETURN VALUE"
-If the connection or binding succeeds, zero is returned. On error, \-1 is
-returned, and
+.I sockaddr
+set to
+.BR AF_UNSPEC
+(supported on Linux since kernel 2.2).
+.SH RETURN VALUE
+If the connection or binding succeeds, zero is returned.
+On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
-The following are general socket errors only. There may be other
-domain-specific error codes.
+The following are general socket errors only.
+There may be other domain-specific error codes.
.TP
.B EACCES
-For Unix domain sockets, which are identified by pathname:
+For UNIX domain sockets, which are identified by pathname:
Write permission is denied on the socket file,
or search permission is denied for one of the directories
in the path prefix.
(See also
-.BR path_resolution (2).)
+.BR path_resolution (7).)
.TP
-.B EACCES, EPERM
-The user tried to connect to a broadcast address without having the socket
+.BR EACCES ", " EPERM
+The user tried to connect to a broadcast address without having the socket
broadcast flag enabled or the connection request failed because of a local
firewall rule.
.TP
Local address is already in use.
.TP
.B EAFNOSUPPORT
-The passed address didn't have the correct address family in its
+The passed address didn't have the correct address family in its
.I sa_family
field.
.TP
.B EAGAIN
-No more free local ports or insufficient entries in the routing cache. For
-.B PF_INET
-see the
-.B net.ipv4.ip_local_port_range
-sysctl in
-.BR ip (7)
-on how to increase the number of local ports.
+No more free local ports or insufficient entries in the routing cache.
+For
+.B AF_INET
+see the description of
+.I /proc/sys/net/ipv4/ip_local_port_range
+.BR ip (7)
+for information on how to increase the number of local ports.
.TP
.B EALREADY
-The socket is non-blocking and a previous connection attempt has not yet
+The socket is nonblocking and a previous connection attempt has not yet
been completed.
.TP
.B EBADF
The file descriptor is not a valid index in the descriptor table.
.TP
.B ECONNREFUSED
-No one listening on the remote address.
+No-one listening on the remote address.
.TP
.B EFAULT
The socket structure address is outside the user's address space.
.TP
.B EINPROGRESS
-The socket is non-blocking and the connection cannot be completed
-immediately. It is possible to
+The socket is nonblocking and the connection cannot be completed
+immediately.
+It is possible to
+.BR select (2)
+or
+.BR poll (2)
+for completion by selecting the socket for writing.
+After
.BR select (2)
-or
-.BR poll (2)
-for completion by selecting the socket for writing. After
-.B select
indicates writability, use
.BR getsockopt (2)
-to read the
+to read the
.B SO_ERROR
-option at level
+option at level
.B SOL_SOCKET
-to determine whether
+to determine whether
.BR connect ()
-completed successfully
+completed successfully
.RB ( SO_ERROR
-is zero) or unsuccessfully
+is zero) or unsuccessfully
.RB ( SO_ERROR
-is one of the usual error codes listed here,
+is one of the usual error codes listed here,
explaining the reason for the failure).
.TP
+.B EINTR
+The system call was interrupted by a signal that was caught; see
+.BR signal (7).
+.\" For TCP, the connection will complete asynchronously.
+.\" See http://lkml.org/lkml/2005/7/12/254
+.TP
.B EISCONN
The socket is already connected.
.TP
The file descriptor is not associated with a socket.
.TP
.B ETIMEDOUT
-Timeout while attempting connection. The server may be too
-busy to accept new connections. Note that for IP sockets the timeout may
+Timeout while attempting connection.
+The server may be too
+busy to accept new connections.
+Note that for IP sockets the timeout may
be very long when syncookies are enabled on the server.
-.SH "CONFORMING TO"
-SVr4, 4.4BSD (the
+.SH CONFORMING TO
+SVr4, 4.4BSD, (the
.BR connect ()
-function first appeared in BSD 4.2). SVr4 documents the additional
-general error codes
-.BR EADDRNOTAVAIL ,
-.BR EINVAL ,
-.BR EAFNOSUPPORT ,
-.BR EALREADY ,
-.BR EINTR ,
-.BR EPROTOTYPE ,
-and
-.BR ENOSR .
-It also
-documents many additional error conditions not described here.
-.SH NOTE
+function first appeared in 4.2BSD), POSIX.1-2001.
+.\" SVr4 documents the additional
+.\" general error codes
+.\" .BR EADDRNOTAVAIL ,
+.\" .BR EINVAL ,
+.\" .BR EAFNOSUPPORT ,
+.\" .BR EALREADY ,
+.\" .BR EINTR ,
+.\" .BR EPROTOTYPE ,
+.\" and
+.\" .BR ENOSR .
+.\" It also
+.\" documents many additional error conditions not described here.
+.SH NOTES
+POSIX.1-2001 does not require the inclusion of
+.IR <sys/types.h> ,
+and this header file is not required on Linux.
+However, some historical (BSD) implementations required this header
+file, and portable applications are probably wise to include it.
+
The third argument of
.BR connect ()
is in reality an
.I int
-(and this is what BSD 4.* and libc4 and libc5 have).
-Some POSIX confusion resulted in the present
+(and this is what 4.x BSD and libc4 and libc5 have).
+Some POSIX confusion resulted in the present
.IR socklen_t ,
also used by glibc.
See also
.BR accept (2).
-.SH BUGS
-Unconnecting a socket by calling
+.SH EXAMPLE
+An example of the use of
.BR connect ()
-with a
-.B AF_UNSPEC
-address is not yet implemented.
-.SH "SEE ALSO"
+is shown in
+.BR getaddrinfo (3).
+.SH SEE ALSO
.BR accept (2),
.BR bind (2),
.BR getsockname (2),
.BR listen (2),
-.BR path_resolution (2),
-.BR socket (2)
+.BR socket (2),
+.BR path_resolution (7)
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