connect.2

早期freebsd实现

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.\"     @(#)connect.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt CONNECT 2
.Os BSD 4.2
.Sh NAME
.Nm connect
.Nd initiate a connection on a socket
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/socket.h>
.Ft int
.Fn connect "int s" "struct sockaddr *name" "int 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.
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.
.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 EADDRNOTAVAILABB
.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
for completion by selecting the socket for writing.
.It Bq Er EALREADY
The socket is non-blocking
and a previous connection attempt
has not yet been completed.
.El
.Pp
The following errors are specific to connecting names in the UNIX domain.
These errors may not apply in future versions of the UNIX IPC domain.
.Bl -tag -width EADDRNOTAVAILABB
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er EINVAL
The pathname contains a character with the high-order bit set.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 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.
.It Bq Er EACCES
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 select 2 ,
.Xr socket 2 ,
.Xr getsockname 2
.Sh HISTORY
The
.Nm
function call appeared in
.Bx 4.2 .