#### 16.3.2 Setting the Address of a Socket

Use the `bind` function to assign an address to a socket. The prototype for `bind` is in the header file `sys/socket.h`. For examples of use, see Local Socket Example, or see Inet Example.

— Function: int bind (int socket, struct sockaddr *addr, socklen_t length)

> Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

> The `bind` function assigns an address to the socket socket. The addr and length arguments specify the address; the detailed format of the address depends on the namespace. The first part of the address is always the format designator, which specifies a namespace, and says that the address is in the format of that namespace.

> The return value is `0` on success and `-1` on failure. The following `errno` error conditions are defined for this function:

> `EBADF`
>   The socket argument is not a valid file descriptor.
> `ENOTSOCK`
>   The descriptor socket is not a socket.
> `EADDRNOTAVAIL`
>   The specified address is not available on this machine.
> `EADDRINUSE`
>   Some other socket is already using the specified address.
> `EINVAL`
>   The socket socket already has an address.
> `EACCES`
>   You do not have permission to access the requested address. (In the Internet domain, only the super-user is allowed to specify a port number in the range 0 through `IPPORT_RESERVED` minus one; see Ports.)

> Additional conditions may be possible depending on the particular namespace of the socket.