1.\" $NetBSD: connect.2,v 1.29 2021/03/28 03:29:31 dholland Exp $ 2.\" 3.\" Copyright (c) 1983, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)connect.2 8.1 (Berkeley) 6/4/93 31.\" 32.Dd March 27, 2021 33.Dt CONNECT 2 34.Os 35.Sh NAME 36.Nm connect 37.Nd initiate a connection on a socket 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/socket.h 42.Ft int 43.Fn connect "int s" "const struct sockaddr *name" "socklen_t namelen" 44.Sh DESCRIPTION 45The parameter 46.Fa s 47is a socket. 48If it is of type 49.Dv SOCK_DGRAM , 50this call specifies the peer with which the socket is to be associated; 51this address is that to which datagrams are to be sent, 52and the only address from which datagrams are to be received. 53If the socket is of type 54.Dv SOCK_STREAM , 55this call attempts to make a connection to 56another socket. 57The other socket is specified by 58.Fa name , 59which is an address in the communications space of the socket. 60.Fa namelen 61indicates the amount of space pointed to by 62.Fa name , 63in bytes. 64Each communications space interprets the 65.Fa name 66parameter in its own way. 67Generally, stream sockets may successfully 68.Fn connect 69only once; datagram sockets may use 70.Fn connect 71multiple times to change their association. 72Datagram sockets may dissolve the association 73by connecting to an invalid address, such as a null address. 74.Pp 75If a 76.Fn connect 77call is interrupted by a signal, it will return with errno set to 78.Er EINTR 79and the connection attempt will proceed as if the socket was non-blocking. 80Subsequent calls to 81.Fn connect 82will set errno to 83.Er EALREADY . 84.Sh RETURN VALUES 85If the connection or binding succeeds, 0 is returned. 86Otherwise a \-1 is returned, and a more specific error 87code is stored in 88.Va errno . 89.Sh ERRORS 90The 91.Fn connect 92call fails if: 93.Bl -tag -width Er 94.It Bq Er EBADF 95.Fa s 96is not a valid descriptor. 97.It Bq Er ENOTSOCK 98.Fa s 99is a descriptor for a file, not a socket. 100.It Bq Er EINVAL 101The socket address length passed was outside the allowable range. 102.It Bq Er EADDRNOTAVAIL 103The specified address is not available on this machine. 104.It Bq Er EAFNOSUPPORT 105Addresses in the specified address family cannot be used with this socket. 106.It Bq Er EISCONN 107The socket is already connected. 108.It Bq Er ETIMEDOUT 109Connection establishment timed out without establishing a connection. 110.It Bq Er ECONNREFUSED 111The attempt to connect was forcefully rejected. 112.It Bq Er ENETUNREACH 113The network isn't reachable from this host. 114.It Bq Er EADDRINUSE 115The address is already in use. 116.It Bq Er EFAULT 117The 118.Fa name 119parameter specifies an area outside 120the process address space. 121.It Bq Er EINPROGRESS 122The socket is non-blocking and the connection cannot be completed immediately. 123It is possible to 124.Xr select 2 125or 126.Xr poll 2 127for completion by selecting or polling the socket for writing. 128The success or failure of the connect operation may be determined by using 129.Xr getsockopt 2 130to read the socket error status with the 131.Dv SO_ERROR 132option at the 133.Dv SOL_SOCKET 134level. 135The returned socket error status is zero on success, or one of the 136error codes listed here on failure. 137.It Bq Er EALREADY 138Either the socket is non-blocking mode or a previous call to 139.Fn connect 140was interrupted by a signal, and the connection attempt has not yet 141been completed. 142.It Bq Er EINTR 143The connection attempt was interrupted by a signal. 144.El 145.Pp 146The following errors are specific to connecting names in the 147.Ux 148domain. 149These errors may not apply in future versions of the 150.Ux 151IPC domain. 152.Bl -tag -width Er 153.It Bq Er ENOTDIR 154A component of the path prefix is not a directory. 155.It Bq Er ENAMETOOLONG 156A component of a pathname exceeded 157.Brq Dv NAME_MAX 158characters, or an entire path name exceeded 159.Brq Dv PATH_MAX 160characters. 161.It Bq Er ENOENT 162The named socket does not exist. 163.It Bq Er EACCES 164Search permission is denied for a component of the path prefix, or 165write access to the named socket is denied. 166.It Bq Er ELOOP 167Too many symbolic links were encountered in translating the pathname. 168.El 169.Sh SEE ALSO 170.Xr accept 2 , 171.Xr getsockname 2 , 172.Xr getsockopt 2 , 173.Xr poll 2 , 174.Xr select 2 , 175.Xr socket 2 176.Sh HISTORY 177The 178.Fn connect 179function call appeared in 180.Bx 4.2 . 181