Closing a Socket - The GNU C Library

Next: Socket Pairs, Previous: Creating a Socket, Up: Open/Close Sockets

#### 16.8.2 Closing a Socket

When you have finished using a socket, you can simply close its file descriptor with `close`; see Opening and Closing Files. If there is still data waiting to be transmitted over the connection, normally `close` tries to complete this transmission. You can control this behavior using the `SO_LINGER` socket option to specify a timeout period; see Socket Options.

You can also shut down only reception or transmission on a connection by calling `shutdown`, which is declared in `sys/socket.h`.

— Function: int shutdown (int socket, int how)

> The `shutdown` function shuts down the connection of socket socket. The argument how specifies what action to perform:

> `0`
>   Stop receiving data for this socket. If further data arrives, reject it.
> `1`
>   Stop trying to transmit data from this socket. Discard any data waiting to be sent. Stop looking for acknowledgement of data already sent; don't retransmit it if it is lost.
> `2`
>   Stop both reception and transmission.

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

> `EBADF`
>   socket is not a valid file descriptor.
> `ENOTSOCK`
>   socket is not a socket.
> `ENOTCONN`
>   socket is not connected.