## nng_close

Close socket.

### Synopsis

```c
#include <nng/nng.h>

int nng_close(nng_socket s);
```

### Description

The `nng_close` function closes the supplied socket, _s_.
Messages that have been submitted for sending may be flushed or delivered, depending upon the transport.

Further attempts to use the socket after this call returns will result in `NNG_ECLOSED`.
Threads waiting for operations on the socket when this call is executed may also return with an `NNG_ECLOSED` result.

NOTE: Closing the socket while data is in transmission will likely lead to loss of that data.
There is no automatic linger or flush to ensure that the socket send buffers have completely transmitted.
It is recommended to wait a brief period after calling xref:nng_send.adoc[`nng_send`] or similar functions, before calling this function.

### Return Values

This function returns 0 on success, and non-zero otherwise.

### Errors

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`NNG_ECLOSED`:: The socket _s_ is already closed or was never opened.
