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CONNECT(3P)                POSIX Programmer's Manual               CONNECT(3P)

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.
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 identifies 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  pro-
       tocol, 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,  con-
       nect()  shall block for up to an unspecified timeout interval until the
       connection is established. If the timeout interval expires  before  the
       connection  is  established,  connect()  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 asynchronously. Subse-
       quent  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 indicate that the file descriptor for the socket is ready
       for writing.
       The socket in use may require the process to  have  appropriate  privi-
       leges to use the connect() 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 specified 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 deliv-
              ery of a signal that was caught; the connection shall be  estab-
              lished asynchronously.
       EISCONN
              The  specified  socket  is  connection-mode  and is already con-
              nected.
       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 original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                          CONNECT(3P)