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.\"     @(#)connect.2	8.1 (Berkeley) 6/4/93
.\"
.Dd May 18, 2004
.Dt CONNECT 2
.Os
.Sh NAME
.Nm connect
.Nd initiate a connection on a socket
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/socket.h
.Ft int
.Fn connect "int s" "const struct sockaddr *name" "socklen_t namelen"
.Sh DESCRIPTION
The parameter
.Fa s
is a socket.
If it is of type
.Dv SOCK_DGRAM ,
this call specifies the peer with which the socket is to be associated;
this address is that to which datagrams are to be sent,
and the only address from which datagrams are to be received.
If the socket is of type
.Dv SOCK_STREAM ,
this call attempts to make a connection to
another socket.
The other socket is specified by
.Fa name ,
which is an address in the communications space of the socket.
.Fa namelen
indicates the amount of space pointed to by
.Fa name ,
in bytes.
Each communications space interprets the
.Fa name
parameter in its own way.
Generally, stream sockets may successfully
.Fn connect
only once; datagram sockets may use
.Fn connect
multiple times to change their association.
Datagram sockets may dissolve the association
by connecting to an invalid address, such as a null address.
.Pp
If a
.Fn connect
call is interrupted by a signal, it will return with errno set to
.Er EINTR
and the connection attempt will proceed as if the socket was non-blocking.
Subsequent calls to
.Fn connect
will set errno to
.Er EALREADY .
.Sh RETURN VALUES
If the connection or binding succeeds, 0 is returned.
Otherwise a \-1 is returned, and a more specific error
code is stored in
.Va errno .
.Sh ERRORS
The
.Fn connect
call fails if:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa s
is not a valid descriptor.
.It Bq Er ENOTSOCK
.Fa s
is a descriptor for a file, not a socket.
.It Bq Er EADDRNOTAVAIL
The specified address is not available on this machine.
.It Bq Er EAFNOSUPPORT
Addresses in the specified address family cannot be used with this socket.
.It Bq Er EISCONN
The socket is already connected.
.It Bq Er ETIMEDOUT
Connection establishment timed out without establishing a connection.
.It Bq Er ECONNREFUSED
The attempt to connect was forcefully rejected.
.It Bq Er ENETUNREACH
The network isn't reachable from this host.
.It Bq Er EADDRINUSE
The address is already in use.
.It Bq Er EFAULT
The
.Fa name
parameter specifies an area outside
the process address space.
.It Bq Er EINPROGRESS
The socket is non-blocking and the connection cannot be completed immediately.
It is possible to
.Xr select 2
or
.Xr poll 2
for completion by selecting or polling the socket for writing.
The success or failure of the connect operation may be determined by using
.Xr getsockopt 2
to read the socket error status with the
.Dv SO_ERROR
option at the
.Dv SOL_SOCKET
level.
The returned socket error status is zero on success, or one of the
error codes listed here on failure.
.It Bq Er EALREADY
Either the socket is non-blocking mode or a previous call to
.Fn connect
was interrupted by a signal, and the connection attempt has not yet
been completed.
.It Bq Er EINTR
The connection attempt was interrupted by a signal.
.El
.Pp
The following errors are specific to connecting names in the
.Ux
domain.
These errors may not apply in future versions of the
.Ux
IPC domain.
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded
.Brq Dv NAME_MAX
characters, or an entire path name exceeded
.Brq Dv PATH_MAX
characters.
.It Bq Er ENOENT
The named socket does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix, or
write access to the named socket is denied.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr getsockname 2 ,
.Xr getsockopt 2 ,
.Xr poll 2 ,
.Xr select 2 ,
.Xr socket 2
.Sh HISTORY
The
.Fn connect
function call appeared in
.Bx 4.2 .