# Socket

## NAME

Socket - Bidirectional streaming IPC transport

## SYNOPSIS

Sockets are a bidirectional stream transport. Unlike channels, sockets
only move data (not handles).

## DESCRIPTION

Data is written into one end of a socket via *zx_socket_write* and
read from the opposing end via *zx_socket_read*.

Upon creation, both ends of the socket are writable and readable. Via the
**ZX_SOCKET_SHUTDOWN_READ** and **ZX_SOCKET_SHUTDOWN_WRITE** options to
*zx_socket_shutdown*, one end of the socket can be closed for reading and/or
writing.

## PROPERTIES

The following properties may be queried from a socket object:

**ZX_PROP_SOCKET_RX_THRESHOLD** size of the read threshold of a socket, in
bytes. When the bytes queued on the socket (available for reading) is equal to
or greater than this value, the ZX_SOCKET_READ_THRESHOLD signal is asserted.
Read threshold signalling is disabled by default (and when set, writing
a value of 0 for this property disables it).

**ZX_PROP_SOCKET_TX_THRESHOLD** size of the write threshold of a socket,
in bytes. When the space available for writing on the socket is equal to or
greater than this value, the ZX_SOCKET_WRITE_THRESHOLD signal is asserted.
Write threshold signalling is disabled by default (and when set, writing a
value of 0 for this property disables it).

From the point of view of a socket handle, the receive buffer contains the data
that is readable via **zx_socket_read**() from that handle (having been written
from the opposing handle), and the transmit buffer contains the data that is
written via **zx_socket_write**() to that handle (and readable from the opposing
handle).

## SIGNALS

The following signals may be set for a socket object:

**ZX_SOCKET_READABLE** data is available to read from the socket

**ZX_SOCKET_WRITABLE** data may be written to the socket

**ZX_SOCKET_PEER_CLOSED** the other endpoint of this socket has
been closed.

**ZX_SOCKET_PEER_WRITE_DISABLED** writing is disabled permanently for the other
endpoint either because of passing **ZX_SOCKET_SHUTDOWN_READ** to this endpoint
or passing **ZX_SOCKET_SHUTDOWN_WRITE** to the peer. Reads on a socket endpoint
with this signal raised will succeed so long as there is data in the socket that
was written before writing was disabled.

**ZX_SOCKET_WRITE_DISABLED** writing is disabled permanently for this endpoint
either because of passing **ZX_SOCKET_SHUTDOWN_WRITE** to this endpoint or
passing **ZX_SOCKET_SHUTDOWN_READ** to the peer.

**ZX_SOCKET_CONTROL_READABLE** data is available to read from the
socket control plane.

**ZX_SOCKET_CONTROL_WRITABLE** data may be written to the socket control plane.

**ZX_SOCKET_SHARE** a socket may be sent via *zx_socket_share*.

**ZX_SOCKET_ACCEPT** a socket may be received via *zx_socket_accept*.

**ZX_SOCKET_READ_THRESHOLD** data queued up on socket for reading exceeds
the read threshold.

**ZX_SOCKET_WRITE_THRESHOLD** space available on the socket for writing exceeds
the write threshold.

## SYSCALLS

+ [socket_accept](../syscalls/socket_accept.md) - receive a socket via a socket
+ [socket_create](../syscalls/socket_create.md) - create a new socket
+ [socket_read](../syscalls/socket_read.md) - read data from a socket
+ [socket_share](../syscalls/socket_share.md) - share a socket via a socket
+ [socket_shutdown](../syscalls/socket_shutdown.md) - prevent reading or writing
+ [socket_write](../syscalls/socket_write.md) - write data to a socket