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Linux 2.6 - man page for connect (linux section 3posix)

CONNECT(P)			    POSIX Programmer's Manual			       CONNECT(P)

NAME
       connect - connect a socket

SYNOPSIS
       #include <sys/socket.h>

       int connect(int socket, const struct sockaddr *address,
	      socklen_t address_len);

DESCRIPTION
       The  connect() function shall attempt to make a connection on a socket. The function takes
       the following arguments:

       socket Specifies the file descriptor associated with the socket.

       address
	      Points to a sockaddr structure containing the peer address.  The length and  format
	      of the address depend on the address family of the socket.

       address_len
	      Specifies the length of the sockaddr structure pointed to by the address argument.

       If the socket has not already been bound to a local address, connect() shall bind it to an
       address which, unless the socket's address family is AF_UNIX, is an unused local address.

       If the initiating socket is not connection-mode, then connect()	shall  set  the  socket's
       peer  address, and no connection is made. For SOCK_DGRAM sockets, the peer address identi-
       fies where all datagrams are sent on subsequent send() functions, and  limits  the  remote
       sender for subsequent recv() functions. If address is a null address for the protocol, the
       socket's peer address shall be reset.

       If the initiating socket is connection-mode, then connect() shall attempt to  establish	a
       connection  to  the address specified by the address argument. If the connection cannot be
       established immediately and O_NONBLOCK is not set for the file descriptor for the  socket,
       connect()  shall  block	for up to an unspecified timeout interval until the connection is
       established. If the timeout interval expires before the connection  is  established,  con-
       nect() shall fail and the connection attempt shall be aborted. If connect() is interrupted
       by a signal that is caught while blocked waiting  to  establish	a  connection,	connect()
       shall  fail and set errno to [EINTR], but the connection request shall not be aborted, and
       the connection shall be established asynchronously.

       If the connection cannot be established immediately and O_NONBLOCK is  set  for	the  file
       descriptor  for	the  socket, connect() shall fail and set errno to [EINPROGRESS], but the
       connection request shall not be aborted, and the connection  shall  be  established  asyn-
       chronously.  Subsequent	calls  to connect() for the same socket, before the connection is
       established, shall fail and set errno to [EALREADY].

       When the connection has been established asynchronously, select() and poll()  shall  indi-
       cate that the file descriptor for the socket is ready for writing.

       The  socket  in use may require the process to have appropriate privileges to use the con-
       nect() function.

RETURN VALUE
       Upon successful completion, connect() shall return 0; otherwise, -1 shall be returned  and
       errno set to indicate the error.

ERRORS
       The connect() function shall fail if:

       EADDRNOTAVAIL
	      The specified address is not available from the local machine.

       EAFNOSUPPORT
	      The  specified  address is not a valid address for the address family of the speci-
	      fied socket.

       EALREADY
	      A connection request is already in progress for the specified socket.

       EBADF  The socket argument is not a valid file descriptor.

       ECONNREFUSED
	      The target address was not listening for	connections  or  refused  the  connection
	      request.

       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.

       EINTR  The attempt to establish a connection was interrupted by delivery of a signal  that
	      was caught; the connection shall be established asynchronously.

       EISCONN
	      The specified socket is connection-mode and is already connected.

       ENETUNREACH
	      No route to the network is present.

       ENOTSOCK
	      The socket argument does not refer to a socket.

       EPROTOTYPE
	      The  specified  address has a different type than the socket bound to the specified
	      peer address.

       ETIMEDOUT
	      The attempt to connect timed out before a connection was made.

       If the address family of the socket is AF_UNIX, then connect() shall fail if:

       EIO    An I/O error occurred while reading from or writing to the file system.

       ELOOP  A loop exists in symbolic links encountered during resolution of	the  pathname  in
	      address.

       ENAMETOOLONG
	      A  component  of	a  pathname exceeded {NAME_MAX} characters, or an entire pathname
	      exceeded {PATH_MAX} characters.

       ENOENT A component of the pathname does not name an existing file or the  pathname  is  an
	      empty string.

       ENOTDIR
	      A component of the path prefix of the pathname in address is not a directory.

       The connect() function may fail if:

       EACCES Search  permission is denied for a component of the path prefix; or write access to
	      the named socket is denied.

       EADDRINUSE
	      Attempt to establish a connection that uses addresses that are already in use.

       ECONNRESET
	      Remote host reset the connection request.

       EHOSTUNREACH
	      The destination host cannot be reached (probably because the  host  is  down  or	a
	      remote router cannot reach it).

       EINVAL The  address_len	argument is not a valid length for the address family; or invalid
	      address family in the sockaddr structure.

       ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during  resolution  of  the
	      pathname in address.

       ENAMETOOLONG
	      Pathname resolution of a symbolic link produced an intermediate result whose length
	      exceeds {PATH_MAX}.

       ENETDOWN
	      The local network interface used to reach the destination is down.

       ENOBUFS
	      No buffer space is available.

       EOPNOTSUPP
	      The socket is listening and cannot be connected.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       If connect() fails, the state of  the  socket  is  unspecified.	 Conforming  applications
       should close the file descriptor and create a new socket before attempting to reconnect.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       accept()  ,  bind()  , close() , getsockname() , poll() , select() , send() , shutdown() ,
       socket() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/socket.h>

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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				       CONNECT(P)


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