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64 .\" Modified Mon Oct 21 23:05:29 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
65 .\" Modified 1998 by Andi Kleen
66 .\" $Id: bind.2,v 1.3 1999/04/23 19:56:07 freitag Exp $
67 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
69 .TH BIND 2 2019-03-06 "Linux" "Linux Programmer's Manual"
71 bind \- bind a name to a socket
74 .BR "#include <sys/types.h>" " /* See NOTES */"
75 .B #include <sys/socket.h>
77 .BI "int bind(int " sockfd ", const struct sockaddr *" addr ,
78 .BI " socklen_t " addrlen );
81 When a socket is created with
83 it exists in a name space (address family) but has no address assigned to it.
85 assigns the address specified by
87 to the socket referred to by the file descriptor
90 specifies the size, in bytes, of the address structure pointed to by
92 Traditionally, this operation is called \(lqassigning a name to a socket\(rq.
94 It is normally necessary to assign a local address using
98 socket may receive connections (see
101 The rules used in name binding vary between address families.
102 Consult the manual entries in Section 7 for detailed information.
132 The actual structure passed for the
134 argument will depend on the address family.
137 structure is defined as something like:
142 sa_family_t sa_family;
148 The only purpose of this structure is to cast the structure
151 in order to avoid compiler warnings.
154 On success, zero is returned.
155 On error, \-1 is returned, and
157 is set appropriately.
161 .\" e.g., privileged port in AF_INET domain
162 The address is protected, and the user is not the superuser.
165 The given address is already in use.
168 (Internet domain sockets)
169 The port number was specified as zero in the socket address structure,
170 but, upon attempting to bind to an ephemeral port,
171 it was determined that all port numbers in the ephemeral port range
172 are currently in use.
173 See the discussion of
174 .I /proc/sys/net/ipv4/ip_local_port_range
179 is not a valid file descriptor.
182 The socket is already bound to an address.
183 .\" This may change in the future: see
184 .\" .I linux/unix/sock.c for details.
190 is not a valid address for this socket's domain.
195 does not refer to a socket.
197 The following errors are specific to UNIX domain
202 Search permission is denied on a component of the path prefix.
204 .BR path_resolution (7).)
207 A nonexistent interface was requested or the requested
208 address was not local.
212 points outside the user's accessible address space.
215 Too many symbolic links were encountered in resolving
223 A component in the directory prefix of the socket pathname does not exist.
226 Insufficient kernel memory was available.
229 A component of the path prefix is not a directory.
232 The socket inode would reside on a read-only filesystem.
234 POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD
236 first appeared in 4.2BSD).
237 .\" SVr4 documents an additional
239 .\" general error condition, and
244 .\" UNIX-domain error conditions.
246 POSIX.1 does not require the inclusion of
248 and this header file is not required on Linux.
249 However, some historical (BSD) implementations required this header
250 file, and portable applications are probably wise to include it.
252 For background on the
257 The transparent proxy options are not described.
258 .\" FIXME Document transparent proxy options
260 An example of the use of
262 with Internet domain sockets can be found in
265 The following example shows how to bind a stream socket in the UNIX
267 domain, and accept connections:
268 .\" listen.7 refers to this example.
269 .\" accept.7 refers to this example.
270 .\" unix.7 refers to this example.
273 #include <sys/socket.h>
279 #define MY_SOCK_PATH "/somepath"
280 #define LISTEN_BACKLOG 50
282 #define handle_error(msg) \e
283 do { perror(msg); exit(EXIT_FAILURE); } while (0)
286 main(int argc, char *argv[])
289 struct sockaddr_un my_addr, peer_addr;
290 socklen_t peer_addr_size;
292 sfd = socket(AF_UNIX, SOCK_STREAM, 0);
294 handle_error("socket");
296 memset(&my_addr, 0, sizeof(struct sockaddr_un));
297 /* Clear structure */
298 my_addr.sun_family = AF_UNIX;
299 strncpy(my_addr.sun_path, MY_SOCK_PATH,
300 sizeof(my_addr.sun_path) \- 1);
302 if (bind(sfd, (struct sockaddr *) &my_addr,
303 sizeof(struct sockaddr_un)) == \-1)
304 handle_error("bind");
306 if (listen(sfd, LISTEN_BACKLOG) == \-1)
307 handle_error("listen");
309 /* Now we can accept incoming connections one
310 at a time using accept(2) */
312 peer_addr_size = sizeof(struct sockaddr_un);
313 cfd = accept(sfd, (struct sockaddr *) &peer_addr,
316 handle_error("accept");
318 /* Code to deal with incoming connection(s)... */
320 /* When no longer required, the socket pathname, MY_SOCK_PATH
321 should be deleted using unlink(2) or remove(3) */
334 .BR path_resolution (7),