.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu) .\" Portions extracted from /usr/include/sys/socket.h, which does not have .\" any authorship information in it. It is probably available under the GPL. .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. 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Raymond .\" Modified 1998 by Andi Kleen .\" $Id: bind.2,v 1.3 1999/04/23 19:56:07 freitag Exp $ .\" Modified 2004-06-23 by Michael Kerrisk .\" .TH BIND 2 2016-12-12 "Linux" "Linux Programmer's Manual" .SH NAME bind \- bind a name to a socket .SH SYNOPSIS .nf .BR "#include " " /* See NOTES */" .B #include .PP .BI "int bind(int " sockfd ", const struct sockaddr *" addr , .BI " socklen_t " addrlen ); .fi .SH DESCRIPTION When a socket is created with .BR socket (2), it exists in a name space (address family) but has no address assigned to it. .BR bind () assigns the address specified by .I addr to the socket referred to by the file descriptor .IR sockfd . .I addrlen specifies the size, in bytes, of the address structure pointed to by .IR addr . Traditionally, this operation is called \(lqassigning a name to a socket\(rq. .PP It is normally necessary to assign a local address using .BR bind () before a .B SOCK_STREAM socket may receive connections (see .BR accept (2)). .PP The rules used in name binding vary between address families. Consult the manual entries in Section 7 for detailed information. For .BR AF_INET , see .BR ip (7); for .BR AF_INET6 , see .BR ipv6 (7); for .BR AF_UNIX , see .BR unix (7); for .BR AF_APPLETALK , see .BR ddp (7); for .BR AF_PACKET , see .BR packet (7); for .BR AF_X25 , see .BR x25 (7); and for .BR AF_NETLINK , see .BR netlink (7). .PP The actual structure passed for the .I addr argument will depend on the address family. The .I sockaddr structure is defined as something like: .PP .in +4n .EX struct sockaddr { sa_family_t sa_family; char sa_data[14]; } .EE .in .PP The only purpose of this structure is to cast the structure pointer passed in .I addr in order to avoid compiler warnings. See EXAMPLE below. .SH RETURN VALUE On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS .TP .B EACCES .\" e.g., privileged port in AF_INET domain The address is protected, and the user is not the superuser. .TP .B EADDRINUSE The given address is already in use. .TP .B EADDRINUSE (Internet domain sockets) The port number was specified as zero in the socket address structure, but, upon attempting to bind to an ephemeral port, it was determined that all port numbers in the ephemeral port range are currently in use. See the discussion of .I /proc/sys/net/ipv4/ip_local_port_range .BR ip (7). .TP .B EBADF .I sockfd is not a valid file descriptor. .TP .B EINVAL The socket is already bound to an address. .\" This may change in the future: see .\" .I linux/unix/sock.c for details. .TP .B EINVAL .I addrlen is wrong, or .I addr is not a valid address for this socket's domain. .TP .B ENOTSOCK The file descriptor .I sockfd does not refer to a socket. .PP The following errors are specific to UNIX domain .RB ( AF_UNIX ) sockets: .TP .B EACCES Search permission is denied on a component of the path prefix. (See also .BR path_resolution (7).) .TP .B EADDRNOTAVAIL A nonexistent interface was requested or the requested address was not local. .TP .B EFAULT .I addr points outside the user's accessible address space. .TP .B ELOOP Too many symbolic links were encountered in resolving .IR addr . .TP .B ENAMETOOLONG .I addr is too long. .TP .B ENOENT A component in the directory prefix of the socket pathname does not exist. .TP .B ENOMEM Insufficient kernel memory was available. .TP .B ENOTDIR A component of the path prefix is not a directory. .TP .B EROFS The socket inode would reside on a read-only filesystem. .SH CONFORMING TO POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD .RB ( bind () first appeared in 4.2BSD). .\" SVr4 documents an additional .\" .B ENOSR .\" general error condition, and .\" additional .\" .B EIO .\" and .\" .B EISDIR .\" UNIX-domain error conditions. .SH NOTES POSIX.1 does not require the inclusion of .IR , and this header file is not required on Linux. However, some historical (BSD) implementations required this header file, and portable applications are probably wise to include it. .PP For background on the .I socklen_t type, see .BR accept (2). .SH BUGS The transparent proxy options are not described. .\" FIXME Document transparent proxy options .SH EXAMPLE An example of the use of .BR bind () with Internet domain sockets can be found in .BR getaddrinfo (3). .PP The following example shows how to bind a stream socket in the UNIX .RB ( AF_UNIX ) domain, and accept connections: .\" listen.7 refers to this example. .\" accept.7 refers to this example. .\" unix.7 refers to this example. .PP .EX #include #include #include #include #include #define MY_SOCK_PATH "/somepath" #define LISTEN_BACKLOG 50 #define handle_error(msg) \\ do { perror(msg); exit(EXIT_FAILURE); } while (0) int main(int argc, char *argv[]) { int sfd, cfd; struct sockaddr_un my_addr, peer_addr; socklen_t peer_addr_size; sfd = socket(AF_UNIX, SOCK_STREAM, 0); if (sfd == \-1) handle_error("socket"); memset(&my_addr, 0, sizeof(struct sockaddr_un)); /* Clear structure */ my_addr.sun_family = AF_UNIX; strncpy(my_addr.sun_path, MY_SOCK_PATH, sizeof(my_addr.sun_path) \- 1); if (bind(sfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr_un)) == \-1) handle_error("bind"); if (listen(sfd, LISTEN_BACKLOG) == \-1) handle_error("listen"); /* Now we can accept incoming connections one at a time using accept(2) */ peer_addr_size = sizeof(struct sockaddr_un); cfd = accept(sfd, (struct sockaddr *) &peer_addr, &peer_addr_size); if (cfd == \-1) handle_error("accept"); /* Code to deal with incoming connection(s)... */ /* When no longer required, the socket pathname, MY_SOCK_PATH should be deleted using unlink(2) or remove(3) */ } .EE .SH SEE ALSO .BR accept (2), .BR connect (2), .BR getsockname (2), .BR listen (2), .BR socket (2), .BR getaddrinfo (3), .BR getifaddrs (3), .BR ip (7), .BR ipv6 (7), .BR path_resolution (7), .BR socket (7), .BR unix (7) .SH COLOPHON This page is part of release 4.16 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.