The Windows Sockets bind function associates a local address with a socket.

int bind (


const struct sockaddr FAR* name,

int namelen




[in] A descriptor identifying an unbound socket.


[in] The address to assign to the socket. The sockaddr structure is defined as follows:

struct sockaddr {

u_short sa_family;

char sa_data[14];


Except for the sa_family field, sockaddr contents are expressed in network byte order.


[in] The length of the name.


This routine is used on an unconnected connectionless or connection-oriented socket, before subsequent connects or listens. When a socket is created with socket, it exists in a name space (address family), but it has no name assigned. bind establishes the local association of the socket by assigning a local name to an unnamed socket.

As an example, in the Internet address family, a name consists of three parts: the address family, a host address, and a port number which identifies the application. In Windows Sockets 2, the name parameter is not strictly interpreted as a pointer to a "sockaddr" structure. It is cast this way for Windows Sockets compatibility. Service Providers are free to regard it as a pointer to a block of memory of size namelen. The first two bytes in this block (corresponding to "sa_family" in the "sockaddr" declaration) must contain the address family that was used to create the socket. Otherwise, an error WSAEFAULT will occur.

If an application does not care what local address is assigned to it, it can specify the manifest constant value ADDR_ANY for the sa_data field of the name parameter. This allows the underlying service provider to use any appropriate network address, potentially simplifying application programming in the presence of multihomed hosts (that is, hosts that have more than one network interface and address). For TCP/IP, if the port is specified as zero, the service provider will assign a unique port to the application with a value between 1024 and 5000. The application can use getsockname after bind to learn the address and the port that has been assigned to it, but note that if the Internet address is equal to INADDR_ANY, getsockname will not necessarily be able to supply the address until the socket is connected, since several addresses can be valid if the host is multihomed.

Return Values

If no error occurs, bind returns zero. Otherwise, it returns SOCKET_ERROR, and a specific error code can be retrieved by calling WSAGetLastError.

Error Codes

A successful WSAStartup must occur before using this function.
The network subsystem has failed.
The specified address is already in use. (See the SO_REUSEADDR socket option under setsockopt.)
The name or the namelen argument is not a valid part of the user address space, the namelen argument is too small, the name argument contains incorrect address format for the associated address family, or the first two bytes of the memory block specified by name does not match the address family associated with the socket descriptor s.
A blocking Windows Sockets 1.1 call is in progress, or the service provider is still processing a callback function.
The socket is already bound to an address.
Not enough buffers available, too many connections.
The descriptor is not a socket.

See Also

, getsockname, listen, setsockopt, socket, WSACancelBlockingCall

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