.\" Copyright (c) 1983, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)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 .Fd #include .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 IMPLEMENTATION NOTES .Pp In the non-threaded library .Fn connect is implemented as the .Va connect syscall. .Pp In the threaded library, the .Va connect syscall is assembled to .Fn _thread_sys_connect and .Fn connect is implemented as a function which locks .Va s for read and write, then calls .Fn _thread_sys_connect . If the call to .Fn _thread_sys_connect would block, a context switch is performed. Before returning, .Fn connect unlocks .Va s . .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 .Fn connect function call appeared in .Bx 4.2 .