connect(2)                                                       connect(2)




 NAME
      connect - initiate a connection on a socket

 SYNOPSIS
      #include <sys/socket.h>

    AF_CCITT only
      #include <x25/x25addrstr.h>

    AF_INET only
      #include <netinet/in.h>

    AF_UNIX only
      #include <sys/un.h>

      int connect(int s, const void *addr, int addrlen);

    _XOPEN_SOURCE_EXTENDED only
      int connect(int s, const struct sockaddr *addr, size_t addrlen);

 DESCRIPTION
      The connect() function initiates a connection on a socket.

      s is a socket descriptor.

      addr is a pointer to a socket address structure containing the address
      of a remote socket to which a connection is to be established.

      addrlen is the size of this address structure.  Since the size of the
      socket address structure varies among socket address families, the
      correct socket address structure should be used with each address
      family (for example, struct sockaddr_in for AF_INET and
      struct sockaddr_un for AF_UNIX).  Typically, the sizeof() function is
      used to pass this value (for example, sizeof(struct sockaddr_in)).

      If the socket is of type SOCK_DGRAM, connect() specifies the peer
      address to which messages are to be sent, and the call returns
      immediately.  Furthermore, this socket can only receive messages sent
      from this address.

      If the socket is of type SOCK_STREAM, connect() attempts to contact
      the remote host to make a connection between the remote socket (peer)
      and the local socket specified by s.  The call normally blocks until
      the connection completes.  If nonblocking mode has been enabled with
      the O_NONBLOCK or O_NDELAY fcntl() flags or the FIOSNBIO ioctl()
      request and the connection cannot be completed immediately, connect()
      returns an error as described below.  In these cases, select() can be
      used on this socket to determine when the connection has completed by
      selecting it for writing.





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 connect(2)                                                       connect(2)




      The connect() system call will complete if remote program has a
      pending listen() even though remote program had not yet issued an
      accept() system call.

      O_NONBLOCK and O_NDELAY are defined in <sys/fcntl.h> and explained in
      fcntl(2), fcntl(5), and socket(7).  FIOSNBIO is defined in
      <sys/ioctl.h> and explained in ioctl(2), ioctl(5), and socket(7).

      If s is a SOCK_STREAM socket that is bound to the same local address
      as another SOCK_STREAM socket, connect() returns [EADDRINUSE] if addr
      is the same as the peer address of that other socket.  This situation
      can only happen if the SO_REUSEADDR option has been set on s, which is
      an AF_INET socket (see getsockopt(2)).

      If the AF_INET socket does not already have a local address bound to
      it (see bind(2)), connect() also binds the socket to a local address
      chosen by the system.

      Generally, stream sockets may successfully connect only once; datagram
      sockets may use connect() multiple times to change the peer address.
      For datagram sockets, a side effect of attempting to connect to some
      invalid address (see ERRORS below) is that the peer address is no
      longer maintained by the system.  An example of an invalid address for
      a datagram socket is addrlen set to 0 and addr set to any value.

    AF_CCITT Only
      Use the x25addrstr struct for the address structure.  The caller must
      know the X.121 address of the DTE to which the connection is to be
      established, including any subaddresses or protocol IDs that may be
      needed.  Refer to af_ccitt(7F) for a detailed description of the
      x25addrstr address structure.  If address-matching by protocol ID,
      specify the protocol ID with the X25_WR_USER_DATA ioctl() call before
      issuing the connect() call.  The X25_WR_USER_DATA ioctl() call is
      described in socketx25(7).

 DEPENDENCIES
    AF_CCITT
      The SO_REUSEADDR option to setsockopt() is not supported for sockets
      in the AF_CCITT address family.

 RETURN VALUE
      connect() returns the following values:

            0   Successful completion.
           -1   Failure.  errno is set to indicate the error.

 ERRORS
      If connect() fails, errno is set to one of the following values.

           [EADDRINUSE]             The specified address is already in use.




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 connect(2)                                                       connect(2)




                                    For datagram sockets, the peer address
                                    is no longer maintained by the system.

           [EADDRNOTAVAIL]          The specified address is not available
                                    on this machine, or the socket is a
                                    TCP/UDP socket and the zero port number
                                    is specified.

                                    For datagram sockets, the peer address
                                    is no longer maintained by the system.

           [EAFNOSUPPORT]           The specified address is not a valid
                                    address for the address family of this
                                    socket.

                                    For datagram sockets, the peer address
                                    is no longer maintained by the system.

           [EALREADY]               Nonblocking I/O is enabled with
                                    O_NONBLOCK, O_NDELAY, or FIOSNBIO, and a
                                    previous connection attempt has not yet
                                    completed.

           [EBADF]                  s is not a valid file descriptor.

           [ECONNREFUSED]           The attempt to connect was forcefully
                                    rejected.

           [EFAULT]                 addr is not a valid pointer.

           [EINPROGRESS]            Nonblocking I/O is enabled using
                                    O_NONBLOCK, O_NDELAY, or FIOSNBIO, and
                                    the connection cannot be completed
                                    immediately.  This is not a failure.
                                    Make the connect() call again a few
                                    seconds later.  Alternatively, wait for
                                    completion by calling select() and
                                    selecting for write.

           [EINTR]                  The connect was interrupted by a signal
                                    before the connect sequence was
                                    complete.  The building of the
                                    connection still takes place, even
                                    though the user is not blocked on the
                                    connect() call.

           [EINVAL]                 The socket has already been shut down or
                                    has a listen() active on it; addrlen is
                                    a bad value; an attempt was made to
                                    connect() an AF_UNIX socket to an NFS-
                                    mounted (remote) name; the X.121 address



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 connect(2)                                                       connect(2)




                                    length is zero, negative, or greater
                                    than 15 digits.

                                    For datagram sockets, if addrlen is a
                                    bad value, the peer address is no longer
                                    maintained by the system.

           [EISCONN]                The socket is already connected.

           [ENETDOWN]               The X.25 interface specified in the addr
                                    struct was found but was not in the
                                    initialized state.  x25ifname field name
                                    is an interface which has been shut down
                                    or never initialized or suffered a power
                                    failure which erased its state
                                    information.

           [ENETUNREACH]            The network is not reachable from this
                                    host.

                                    For AF_CCITT only: X.25 Level 2 is down.
                                    The X.25 link is not working: wires
                                    might be broken, connections are loose
                                    on the interface hoods at the modem, the
                                    modem failed, or noise interfered with
                                    the line for an extremely long period of
                                    time.

           [ENOBUFS]                No buffer space is available.  The
                                    connect() has failed.

           [ENODEV]                 The x25ifname field refers to a
                                    nonexistent interface.

           [ENOSPC]                 All available virtual circuits are in
                                    use.

           [ENOTSOCK]               s is a valid file descriptor, but it is
                                    not a socket.

           [EOPNOTSUPP]             The socket referenced by s does not
                                    support connect().  With X.25 an attempt
                                    was made to issue a connect() call on a
                                    listen() socket.

           [ETIMEDOUT]              Connection establishment timed out
                                    without establishing a connection.  One
                                    reason could be that the connection
                                    requests queue at the remote socket may
                                    be full (see listen(2)).




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 connect(2)                                                       connect(2)




 AUTHOR
      connect() was developed by the University of California, Berkeley.

 FUTURE DIRECTION
      The default behavior in this release is still the classic HP-UX BSD
      Sockets, however it will be changed to X/Open Sockets in some future
      release.  At that time, any HP-UX BSD Sockets behavior which is
      incompatible with X/Open Sockets may be obsoleted.  HP customers are
      advised to migrate their applications to conform to X/Open
      specification( see xopen_networking(7) ).

 SEE ALSO
      accept(2), getsockname(2), select(2), socket(2), af_ccitt(7F),
      socket(7), socketx25(7), xopen_networking(7).








































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