| Standards / Extensions | C or C++ | Dependencies |
|---|---|---|
XPG4.2 |
both |
#define _XOPEN_SOURCE_EXTENDED 1
#include <sys/socket.h>
int bind(int socket, const struct sockaddr *address, socklen_t address_len);#define _OE_SOCKETS
#include <sys/types.h>
#include <sys/socket.h>
int bind(int socket, struct sockaddr *address, int address_len);The socket parameter is a socket descriptor of any type created by calling socket().
The address parameter is a pointer to a buffer containing the name to be bound to socket. The address_len parameter is the size, in bytes, of the buffer pointed to by address. For AF_UNIX, this function creates a file that you later need to unlink besides closing the socket.
Socket Descriptor Created in the AF_INET Domain
struct in_addr
{
ip_addr_t s_addr;
};
struct sockaddr_in {
unsigned char sin_len;
unsigned char sin_family;
unsigned short sin_port;
struct in_addr sin_addr;
unsigned char sin_zero[8];
};The sin_family field must be set to AF_INET.
The sin_port field is set to the port to which the application must bind. It must be specified in network byte order. If sin_port is set to 0, the caller leaves it to the system to assign an available port. The application can call getsockname() to discover the port number assigned.
The sin_addr.s_addr field is set to the Internet address and must be specified in network byte order. On hosts with more than one network interface (called multihomed hosts), a caller can select the interface to which it is to bind. Subsequently, only UDP packets and TCP connection requests from this interface (which match the bound name) are routed to the application. If this field is set to the constant INADDR_ANY, as defined in netinet/in.h, the caller is requesting that the socket be bound to all network interfaces on the host. Subsequently, UDP packets and TCP connections from all interfaces (which match the bound name) are routed to the application. This becomes important when a server offers a service to multiple networks. By leaving the address unspecified, the server can accept all UDP packets and TCP connection requests made for its port, regardless of the network interface on which the requests arrived.
The sin_zero field is not used and must be set to all zeros.
struct sockaddr_in6 {
uint8_t sin6_len;
sa_family_t sin6_family;
in_port_t sin6_port;
uint32_t sin6_flowinfo;
struct in6_addr sin6_addr;
uint32_t sin6_scope_id;
};The sin6_len field is set to the size of this structure. The SIN6_LEN macro is defined to indicate the version of the sockaddr_in6 structure being used.
The sin6_family field identifies this as a sockaddr_in6 structure. This field overlays the sa_family field when the buffer is cast to a sockaddr structure. The value of this field must be AF_INET6.
The sin6_port field contains the 16-bit UDP or TCP port number. This field is used in the same way as the sin_port field of the sockaddr_in structure. The port number is stored in network byte order.
The sin6_flowinfo field is a 32-bit field that contains the traffic class and the flow label.
The sin6_addr field is a single in6_addr structure. This field holds one 128-bit IPv6 address. The address is stored in network byte order.
The sin6_scope_id field is a 32-bit integer that identifies a set of interfaces as appropriate for the scope of the address carried in the sin6_addr field. For a link scope sin6_addr, sin6_scope_id, this would be an interface index. For a site scope sin6_addr, sin6_scope_id, this would be a site identifier.
Socket Descriptor Created in the AF_UNIX Domain
struct sockaddr_un {
unsigned char sun_len;
unsigned char sun_family;
char sun_path[108]; /* pathname */
};The sun_family field is set to AF_UNIX.
Special Behavior for C++
To use this function with C++, you must use the _XOPEN_SOURCE_EXTENDED 1 feature test macro.
If successful, bind() returns 0.
The following are examples of the bind() call. It is a good idea to zero the structure before using it to ensure that the name requested does not set any reserved fields.
AF_INET Domain Example
int rc;
int s;
struct sockaddr_in myname;
/* Bind to a specific interface in the Internet domain */
/* make sure the sin_zero field is cleared */
memset(&myname, 0, sizeof(myname));
myname.sin_family = AF_INET;
myname.sin_addr.s_addr = inet_addr("129.5.24.1");
/* specific interface */
myname.sin_port = htons(1024);
⋮
rc = bind(s, (struct sockaddr *) &myname,
sizeof(myname));
/* Bind to all network interfaces in the Internet domain */
/* make sure the sin_zero field is cleared */
memset(&myname, 0, sizeof(myname));
myname.sin_family = AF_INET;
myname.sin_addr.s_addr = INADDR_ANY; /* specific interface */
myname.sin_port = htons(1024);
⋮
rc = bind(s, (struct sockaddr *) &myname,
sizeof(myname));
/* Bind to a specific interface in the Internet domain.
Let the system choose a port */
/* make sure the sin_zero field is cleared */
memset(&myname, 0, sizeof(myname));
myname.sin_family = AF_INET;
myname.sin_addr.s_addr = inet_addr("129.5.24.1");
/* specific interface */
myname.sin_port = 0;
⋮
rc = bind(s, (struct sockaddr *) &myname,
sizeof(myname));AF_UNIX Domain Example
/* Bind to a name in the UNIX domain */
struct sockaddr_un myname;
char socket_name[]="/tmp/socket.for._";
⋮
memset(&myname, 0, sizeof(myname));
myname.sun_family = AF_UNIX;
strcpy(myname.sun_path,socket_name);
myname.sun_len = sizeof(myname.sun_path);
⋮
rc = bind(s, (struct sockaddr *) &myname, SUN_LEN(&myname));