1BIND(2) Linux Programmer's Manual BIND(2)
2
6 bind - bind a name to a socket
7
9 #include <sys/types.h> /* See NOTES */
10 #include <sys/socket.h>
11 int bind(int sockfd, const struct sockaddr *addr,
13 socklen_t addrlen);
14
16 When a socket is created with socket(2), it exists in a name space
17 (address family) but has no address assigned to it. bind() assigns the
18 address specified by addr to the socket referred to by the file
19 descriptor sockfd. addrlen specifies the size, in bytes, of the
20 address structure pointed to by addr. Traditionally, this operation is
21 called “assigning a name to a socket”.
22 It is normally necessary to assign a local address using bind() before
24 a SOCK_STREAM socket may receive connections (see accept(2)).
25 The rules used in name binding vary between address families. Consult
27 the manual entries in Section 7 for detailed information. For AF_INET,
28 see ip(7); for AF_INET6, see ipv6(7); for AF_UNIX, see unix(7); for
29 AF_APPLETALK, see ddp(7); for AF_PACKET, see packet(7); for AF_X25, see
30 x25(7); and for AF_NETLINK, see netlink(7).
31 The actual structure passed for the addr argument will depend on the
33 address family. The sockaddr structure is defined as something like:
34 struct sockaddr {
36 sa_family_t sa_family;
37 char sa_data[14];
38 }
39 The only purpose of this structure is to cast the structure pointer
41 passed in addr in order to avoid compiler warnings. See EXAMPLE below.
42
44 On success, zero is returned. On error, -1 is returned, and errno is
45 set appropriately.
46
48 EACCES The address is protected, and the user is not the superuser.
49 EADDRINUSE
51 The given address is already in use.
52 EADDRINUSE
54 (Internet domain sockets) The port number was specified as zero
55 in the socket address structure, but, upon attempting to bind to
56 an ephemeral port, it was determined that all port numbers in
57 the ephemeral port range are currently in use. See the discus‐
58 sion of /proc/sys/net/ipv4/ip_local_port_range ip(7).
59 EBADF sockfd is not a valid file descriptor.
61 EINVAL The socket is already bound to an address.
63 EINVAL addrlen is wrong, or addr is not a valid address for this
65 socket's domain.
66 ENOTSOCK
68 The file descriptor sockfd does not refer to a socket.
69 The following errors are specific to UNIX domain (AF_UNIX) sockets:
71 EACCES Search permission is denied on a component of the path prefix.
73 (See also path_resolution(7).)
74 EADDRNOTAVAIL
76 A nonexistent interface was requested or the requested address
77 was not local.
78 EFAULT addr points outside the user's accessible address space.
80 ELOOP Too many symbolic links were encountered in resolving addr.
82 ENAMETOOLONG
84 addr is too long.
85 ENOENT A component in the directory prefix of the socket pathname does
87 not exist.
88 ENOMEM Insufficient kernel memory was available.
90 ENOTDIR
92 A component of the path prefix is not a directory.
93 EROFS The socket inode would reside on a read-only filesystem.
95
97 POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD (bind() first appeared in
98 4.2BSD).
99
101 POSIX.1 does not require the inclusion of <sys/types.h>, and this
102 header file is not required on Linux. However, some historical (BSD)
103 implementations required this header file, and portable applications
104 are probably wise to include it.
105 For background on the socklen_t type, see accept(2).
107
109 The transparent proxy options are not described.
110
112 An example of the use of bind() with Internet domain sockets can be
113 found in getaddrinfo(3).
114 The following example shows how to bind a stream socket in the UNIX
116 (AF_UNIX) domain, and accept connections:
117 #include <sys/socket.h>
119 #include <sys/un.h>
120 #include <stdlib.h>
121 #include <stdio.h>
122 #include <string.h>
123 #define MY_SOCK_PATH "/somepath"
125 #define LISTEN_BACKLOG 50
126 #define handle_error(msg) \
128 do { perror(msg); exit(EXIT_FAILURE); } while (0)
129 int
131 main(int argc, char *argv[])
132 {
133 int sfd, cfd;
134 struct sockaddr_un my_addr, peer_addr;
135 socklen_t peer_addr_size;
136 sfd = socket(AF_UNIX, SOCK_STREAM, 0);
138 if (sfd == -1)
139 handle_error("socket");
140 memset(&my_addr, 0, sizeof(struct sockaddr_un));
142 /* Clear structure */
143 my_addr.sun_family = AF_UNIX;
144 strncpy(my_addr.sun_path, MY_SOCK_PATH,
145 sizeof(my_addr.sun_path) - 1);
146 if (bind(sfd, (struct sockaddr *) &my_addr,
148 sizeof(struct sockaddr_un)) == -1)
149 handle_error("bind");
150 if (listen(sfd, LISTEN_BACKLOG) == -1)
152 handle_error("listen");
153 /* Now we can accept incoming connections one
155 at a time using accept(2) */
156 peer_addr_size = sizeof(struct sockaddr_un);
158 cfd = accept(sfd, (struct sockaddr *) &peer_addr,
159 &peer_addr_size);
160 if (cfd == -1)
161 handle_error("accept");
162 /* Code to deal with incoming connection(s)... */
164 /* When no longer required, the socket pathname, MY_SOCK_PATH
166 should be deleted using unlink(2) or remove(3) */
167 }
168
170 accept(2), connect(2), getsockname(2), listen(2), socket(2), getad‐
171 drinfo(3), getifaddrs(3), ip(7), ipv6(7), path_resolution(7),
172 socket(7), unix(7)
173
175 This page is part of release 5.04 of the Linux man-pages project. A
176 description of the project, information about reporting bugs, and the
177 latest version of this page, can be found at
178 https://www.kernel.org/doc/man-pages/.
179Linux 2019-03-06 BIND(2)