connect - connect a socket
cc [ flag ... ] file ... -lxnet [ library ... ]
#include <sys/socket.h>
int connect(int socket, const struct sockaddr *address,
socklen_t address_len);
The connect() function requests a connection to be made 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() will 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() sets the socket's peer address, but no connection is made.
For SOCK_DGRAM sockets, the peer address identifies where all datagrams are
sent on subsequent send(3XNET) calls, and limits the remote sender
for subsequent recv(3XNET) calls. If address is a null address
for the protocol, the socket's peer address will be reset.
If the initiating socket is connection-mode, then connect()
attempts 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() will
block for up to an unspecified timeout interval until the connection is
established. If the timeout interval expires before the connection is
established, connect() will fail and the connection attempt will be
aborted. If connect() is interrupted by a signal that is caught while
blocked waiting to establish a connection, connect() will fail and
set errno to EINTR, but the connection request will not be
aborted, and the connection will be established asynchronously.
If the connection cannot be established immediately and O_NONBLOCK
is set for the file descriptor for the socket, connect() will fail
and set errno to EINPROGRESS, but the connection request will
not be aborted, and the connection will be established asynchronously.
Subsequent calls to connect() for the same socket, before the
connection is established, will fail and set errno to
EALREADY.
When the connection has been established asynchronously,
select(3C) and poll(2) will indicate 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 connect() function.
If connect() fails, the state of the socket is unspecified. Portable
applications should close the file descriptor and create a new socket before
attempting to reconnect.
Upon successful completion, connect() returns 0. Otherwise, −1 is
returned and errno is set to indicate the error.
The connect() function will 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.
EFAULT
The address parameter can not be accessed.
EINPROGRESS
O_NONBLOCK is set for the file descriptor for the socket
and the connection cannot be immediately established; the connection will be
established asynchronously.
EINTR
The attempt to establish a connection was interrupted by
delivery of a signal that was caught; the connection will 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() will fail if:
EIO
An I/O error occurred while reading from or writing to
the file system.
ELOOP
Too many symbolic links were encountered in translating
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 sockaddr structure.
ENAMETOOLONG
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds PATH_MAX.
ENETDOWN
The local interface used to reach the destination is
down.
ENOBUFS
No buffer space is available.
ENOSR
There were insufficient STREAMS resources available to
complete the operation.
EOPNOTSUPP
The socket is listening and can not be connected.
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE
TYPE |
ATTRIBUTE VALUE |
| Interface Stability |
Standard |
| MT-Level |
MT-Safe |
close(2), poll(2), select(3C), sockaddr(3SOCKET),
accept(3XNET), bind(3XNET), getsockname(3XNET),
send(3XNET), shutdown(3XNET), socket(3XNET),
attributes(7), standards(7)