---
name: "io_uring_prep_socket"
section: "3"
platform: "linux"
package: "liburing"
version: "2.15-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/io_uring_prep_socket"
---

# io\_uring\_prep\_socket(3)

prepare a socket creation request

## NAME

io\_uring\_prep\_socket - prepare a socket creation request

## SYNOPSIS

```
#include <sys/socket.h>
#include <liburing.h>
```

**void io\_uring\_prep\_socket(struct io\_uring\_sqe \****sqe***,**                           **int** *domain***,**                           **int** *type***,**                           **int** *protocol***,**                           **unsigned int** *flags***);**

**void io\_uring\_prep\_socket\_direct(struct io\_uring\_sqe \****sqe***,**                                  **int** *domain***,**                                  **int** *type***,**                                  **int** *protocol***,**                                  **unsigned int** *file\_index***,**                                  **unsigned int** *flags***);**

**void io\_uring\_prep\_socket\_direct\_alloc(struct io\_uring\_sqe \****sqe***,**                                  **int** *domain***,**                                  **int** *type***,**                                  **int** *protocol***,**                                  **unsigned int** *flags***);**

## DESCRIPTION

The [**io\_uring\_prep\_socket**(3)](/io_uring_prep_socket/3.md) function prepares a socket creation request. The submission queue entry *sqe* is setup to use the communication domain defined by *domain* and use the communication type defined by *type* and the protocol set by *protocol*. The *flags* argument are currently unused.

The [**io\_uring\_prep\_socket\_direct**(3)](/io_uring_prep_socket_direct/3.md) helper works just like [**io\_uring\_prep\_socket**(3)](/io_uring_prep_socket/3.md), except it maps the socket to a direct descriptor rather than return a normal file descriptor. The *file\_index* argument should be set to the slot that should be used for this socket.

The [**io\_uring\_prep\_socket\_direct\_alloc**(3)](/io_uring_prep_socket_direct_alloc/3.md) helper works just like [**io\_uring\_prep\_socket\_direct**(3)](/io_uring_prep_socket_direct/3.md), except it allocates a new direct descriptor rather than pass a free slot in. It is equivalent to using [**io\_uring\_prep\_socket\_direct**(3)](/io_uring_prep_socket_direct/3.md) with **IORING\_FILE\_INDEX\_ALLOC** as the *file\_index .* Upon completion, the *res* field of the CQE will return the direct slot that was allocated for the socket.

If the direct variants are used, the application must first have registered a file table using [**io\_uring\_register\_files**(3)](/io_uring_register_files/3.md) of the appropriate size. Once registered, a direct socket request may use any entry in that table, as long as it is within the size of the registered table. If a specified entry already contains a file, the file will first be removed from the table and closed. It's consistent with the behavior of updating an existing file with [**io\_uring\_register\_files\_update**(3)](/io_uring_register_files_update/3.md).

For a direct descriptor socket request, the *file\_index* argument can be set to **IORING\_FILE\_INDEX\_ALLOC**, In this case a free entry in io\_uring file table will be used automatically and the file index will be returned as CQE *res*. **-ENFILE** is otherwise returned if there is no free entries in the io\_uring file table.

These functions prepare an async [**socket**(2)](/socket/2.md) request. See that man page for details.

## RETURN VALUE

None

## ERRORS

The CQE *res* field will contain the result of the operation. See the related man page for details on possible values. Note that where synchronous system calls will return **-1** on failure and set *errno* to the actual error value, io\_uring never uses *errno*. Instead it returns the negated *errno* directly in the CQE *res* field.

## SEE ALSO

[**io\_uring\_get\_sqe**(3)](/io_uring_get_sqe/3.md), [**io\_uring\_submit**(3)](/io_uring_submit/3.md), [**socket**(2)](/socket/2.md)