connect

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].

       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.

       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.

       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(P)