bind Function (Winsock2.h)

Binds a local name (address and port) to a socket.

Syntax


int bind(
  SOCKET            s,
  const SOCKADDR *name,
  int               namelen
);

Parameters

Parameter	Description
`s`	A descriptor that identifies an unbound socket.
`name`	A pointer to a `SOCKADDR` structure that specifies the address and port to associate with the socket `s`. For internet protocols, this is a pointer to a `SOCKADDR_IN` structure.
`namelen`	The size, in bytes, of the structure pointed to by the `name` parameter.

Return Value

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

Remarks

The bind function is used to associate a local address with a socket. When a socket is created with socket, it exists in an unknown name space. A local name must be explicitly assigned by calling bind before the socket can be connected to another socket.

If the socket is of type SOCK_DGRAM, the local address is the address that the datagrams will be sent from. If you do not care about the incoming data, you can bind to the wildcard address (all interfaces).

For connection-oriented protocols like SOCK_STREAM, binding to a specific port is often required for servers to accept incoming connections. Clients can typically bind to an unspecified port, allowing the system to assign a unique ephemeral port.

Important Notes:

Ensure that the SOCKADDR structure is correctly populated with the desired address family, IP address, and port number.
For IPv4, use AF_INET and a SOCKADDR_IN structure.
For IPv6, use AF_INET6 and a SOCKADDR_IN6 structure.
Binding to the wildcard address (0.0.0.0 for IPv4, or :: for IPv6) allows the socket to accept connections on any available network interface.

Windows API Reference