# zx_socket_write

## NAME

socket_write - write data to a socket

## SYNOPSIS

```
#include <zircon/syscalls.h>

zx_status_t zx_socket_write(zx_handle_t handle, uint32_t options,
                            const void* buffer, size_t buffer_size,
                            size_t* actual) {
```

## DESCRIPTION

**socket_write**() attempts to write *buffer_size* bytes to the socket specified
by *handle*. The pointer to *bytes* may be NULL if *buffer_size* is zero.

If *buffer_size* is zero, a bitwise combination of **ZX_SOCKET_SHUTDOWN_READ** and
**ZX_SOCKET_SHUTDOWN_WRITE** can be passed to *options* to disable reading or
writing from a socket endpoint:

 * If **ZX_SOCKET_SHUTDOWN_READ** is passed to *options*, and *buffer_size* is
   0, then reading is disabled for the socket endpoint at *handle*. All data
   buffered in the socket at the time of the call can be read, but further reads
   from this endpoint or writes to the other endpoint of the socket will fail
   with **ZX_ERR_BAD_STATE**.

 * If **ZX_SOCKET_SHUTDOWN_WRITE** is passed to *options*, and *buffer_size* is
   0, then writing is disabled for the socket endpoint at *handle*. Further
   writes to this endpoint or reads from the other endpoint of the socket will
   fail with **ZX_ERR_BAD_STATE**.

If **ZX_SOCKET_CONTROL** is passed to *options*, then **socket_write**()
attempts to write into the socket control plane. A write to the control plane is
never short. If the socket control plane has insufficient space for *buffer*, it
writes nothing and returns **ZX_ERR_OUT_OF_RANGE**.

If a NULL *actual* is passed in, it will be ignored.

A **ZX_SOCKET_STREAM** socket write can be short if the socket does not have
enough space for all of *buffer*. If a non-zero amount of data was written to
the socket, the amount written is returned via *actual* and the call succeeds.
Otherwise, if the socket was already full, the call returns
**ZX_ERR_SHOULD_WAIT** and the client should wait (e.g., with
[object_wait_one](object_wait_one.md) or
[object_wait_async](object_wait_async.md)). For datagram sockets, attempting to
write a packet larger than the socket's capacity will fail with
**ZX_ERR_OUT_OF_RANGE**.

A **ZX_SOCKET_DATAGRAM** socket write is never short. If the socket has
insufficient space for *buffer*, it writes nothing and returns
**ZX_ERR_SHOULD_WAIT**. If the write succeeds, *buffer_size* is returned via
*actual*.

## RIGHTS

TODO(ZX-2399)

## RETURN VALUE

**socket_write**() returns **ZX_OK** on success.

## ERRORS

**ZX_ERR_BAD_HANDLE**  *handle* is not a valid handle.

**ZX_ERR_BAD_STATE**  *options* includes **ZX_SOCKET_CONTROL** and the
socket was not created with **ZX_SOCKET_HAS_CONTROL**.

**ZX_ERR_WRONG_TYPE**  *handle* is not a socket handle.

**ZX_ERR_INVALID_ARGS**  *buffer* is an invalid pointer,
**ZX_SOCKET_SHUTDOWN_READ** and/or **ZX_SOCKET_SHUTDOWN_WRITE** was passed to
*options* but *buffer_size* was not 0, or *options* was not 0 or a combination
or **ZX_SOCKET_SHUTDOWN_READ** and/or **ZX_SOCKET_SHUTDOWN_WRITE**.

**ZX_ERR_ACCESS_DENIED**  *handle* does not have **ZX_RIGHT_WRITE**.

**ZX_ERR_SHOULD_WAIT**  The buffer underlying the socket is full.

**ZX_ERR_OUT_OF_RANGE**  The socket was created with **ZX_SOCKET_DATAGRAM** and
*buffer* is larger than the remaining space in the socket.

**ZX_ERR_BAD_STATE**  Writing has been disabled for this socket endpoint.

**ZX_ERR_PEER_CLOSED**  The other side of the socket is closed.

**ZX_ERR_NO_MEMORY**  Failure due to lack of memory.
There is no good way for userspace to handle this (unlikely) error.
In a future build this error will no longer occur.

## SEE ALSO

[socket_create](socket_create.md),
[socket_read](socket_read.md).