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tildefriends/deps/libuv/docs/src/udp.rst

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.. _udp:
:c:type:`uv_udp_t` --- UDP handle
=================================
UDP handles encapsulate UDP communication for both clients and servers.
Data types
----------
.. c:type:: uv_udp_t
UDP handle type.
.. c:type:: uv_udp_send_t
UDP send request type.
.. c:type:: uv_udp_flags
Flags used in :c:func:`uv_udp_bind` and :c:type:`uv_udp_recv_cb`..
::
enum uv_udp_flags {
/* Disables dual stack mode. */
UV_UDP_IPV6ONLY = 1,
/*
* Indicates message was truncated because read buffer was too small. The
* remainder was discarded by the OS. Used in uv_udp_recv_cb.
*/
UV_UDP_PARTIAL = 2,
/*
* Indicates if SO_REUSEADDR will be set when binding the handle in
* uv_udp_bind.
* This sets the SO_REUSEPORT socket flag on the BSDs and OS X. On other
* Unix platforms, it sets the SO_REUSEADDR flag. What that means is that
* multiple threads or processes can bind to the same address without error
* (provided they all set the flag) but only the last one to bind will receive
* any traffic, in effect "stealing" the port from the previous listener.
*/
UV_UDP_REUSEADDR = 4,
/*
* Indicates that the message was received by recvmmsg, so the buffer provided
* must not be freed by the recv_cb callback.
*/
UV_UDP_MMSG_CHUNK = 8,
/*
* Indicates that the buffer provided has been fully utilized by recvmmsg and
* that it should now be freed by the recv_cb callback. When this flag is set
* in uv_udp_recv_cb, nread will always be 0 and addr will always be NULL.
*/
UV_UDP_MMSG_FREE = 16,
/*
* Indicates if IP_RECVERR/IPV6_RECVERR will be set when binding the handle.
* This sets IP_RECVERR for IPv4 and IPV6_RECVERR for IPv6 UDP sockets on
* Linux. This stops the Linux kernel from suppressing some ICMP error messages
* and enables full ICMP error reporting for faster failover.
* This flag is no-op on platforms other than Linux.
*/
UV_UDP_LINUX_RECVERR = 32,
/*
* Indicates that recvmmsg should be used, if available.
*/
UV_UDP_RECVMMSG = 256
};
.. c:type:: void (*uv_udp_send_cb)(uv_udp_send_t* req, int status)
Type definition for callback passed to :c:func:`uv_udp_send`, which is
called after the data was sent.
.. c:type:: void (*uv_udp_recv_cb)(uv_udp_t* handle, ssize_t nread, const uv_buf_t* buf, const struct sockaddr* addr, unsigned flags)
Type definition for callback passed to :c:func:`uv_udp_recv_start`, which
is called when the endpoint receives data.
* `handle`: UDP handle
* `nread`: Number of bytes that have been received.
0 if there is no more data to read. Note that 0 may also mean that an
empty datagram was received (in this case `addr` is not NULL). < 0 if
a transmission error was detected; if using :man:`recvmmsg(2)` no more
chunks will be received and the buffer can be freed safely.
* `buf`: :c:type:`uv_buf_t` with the received data.
* `addr`: ``struct sockaddr*`` containing the address of the sender.
Can be NULL. Valid for the duration of the callback only.
* `flags`: One or more or'ed UV_UDP_* constants.
The callee is responsible for freeing the buffer, libuv does not reuse it.
The buffer may be a null buffer (where `buf->base` == NULL and `buf->len` == 0)
on error.
When using :man:`recvmmsg(2)`, chunks will have the `UV_UDP_MMSG_CHUNK` flag set,
those must not be freed. If no errors occur, there will be a final callback with
`nread` set to 0, `addr` set to NULL and the buffer pointing at the initially
allocated data with the `UV_UDP_MMSG_CHUNK` flag cleared and the `UV_UDP_MMSG_FREE`
flag set. If a UDP socket error occurs, `nread` will be < 0. In either scenario,
the callee can now safely free the provided buffer.
.. versionchanged:: 1.40.0 added the `UV_UDP_MMSG_FREE` flag.
.. note::
The receive callback will be called with `nread` == 0 and `addr` == NULL when there is
nothing to read, and with `nread` == 0 and `addr` != NULL when an empty UDP packet is
received.
.. c:enum:: uv_membership
Membership type for a multicast address.
::
typedef enum {
UV_LEAVE_GROUP = 0,
UV_JOIN_GROUP
} uv_membership;
Public members
^^^^^^^^^^^^^^
.. c:member:: size_t uv_udp_t.send_queue_size
Number of bytes queued for sending. This field strictly shows how much
information is currently queued.
.. c:member:: size_t uv_udp_t.send_queue_count
Number of send requests currently in the queue awaiting to be processed.
.. c:member:: uv_udp_t* uv_udp_send_t.handle
UDP handle where this send request is taking place.
.. seealso:: The :c:type:`uv_handle_t` members also apply.
API
---
.. c:function:: int uv_udp_init(uv_loop_t* loop, uv_udp_t* handle)
Initialize a new UDP handle. The actual socket is created lazily.
Returns 0 on success.
.. c:function:: int uv_udp_init_ex(uv_loop_t* loop, uv_udp_t* handle, unsigned int flags)
Initialize the handle with the specified flags. The lower 8 bits of the `flags`
parameter are used as the socket domain. A socket will be created for the given domain.
If the specified domain is ``AF_UNSPEC`` no socket is created, just like :c:func:`uv_udp_init`.
The remaining bits can be used to set one of these flags:
* `UV_UDP_RECVMMSG`: if set, and the platform supports it, :man:`recvmmsg(2)` will
be used.
.. versionadded:: 1.7.0
.. versionchanged:: 1.37.0 added the `UV_UDP_RECVMMSG` flag.
.. c:function:: int uv_udp_open(uv_udp_t* handle, uv_os_sock_t sock)
Opens an existing file descriptor or Windows SOCKET as a UDP handle.
Unix only:
The only requirement of the `sock` argument is that it follows the datagram
contract (works in unconnected mode, supports sendmsg()/recvmsg(), etc).
In other words, other datagram-type sockets like raw sockets or netlink
sockets can also be passed to this function.
.. versionchanged:: 1.2.1 the file descriptor is set to non-blocking mode.
.. note::
The passed file descriptor or SOCKET is not checked for its type, but
it's required that it represents a valid datagram socket.
.. c:function:: int uv_udp_bind(uv_udp_t* handle, const struct sockaddr* addr, unsigned int flags)
Bind the UDP handle to an IP address and port.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param addr: `struct sockaddr_in` or `struct sockaddr_in6`
with the address and port to bind to.
:param flags: Indicate how the socket will be bound,
``UV_UDP_IPV6ONLY``, ``UV_UDP_REUSEADDR``, and ``UV_UDP_RECVERR``
are supported.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_connect(uv_udp_t* handle, const struct sockaddr* addr)
Associate the UDP handle to a remote address and port, so every
message sent by this handle is automatically sent to that destination.
Calling this function with a `NULL` `addr` disconnects the handle.
Trying to call `uv_udp_connect()` on an already connected handle will result
in an `UV_EISCONN` error. Trying to disconnect a handle that is not
connected will return an `UV_ENOTCONN` error.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param addr: `struct sockaddr_in` or `struct sockaddr_in6`
with the address and port to associate to.
:returns: 0 on success, or an error code < 0 on failure.
.. versionadded:: 1.27.0
.. c:function:: int uv_udp_getpeername(const uv_udp_t* handle, struct sockaddr* name, int* namelen)
Get the remote IP and port of the UDP handle on connected UDP handles.
On unconnected handles, it returns `UV_ENOTCONN`.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init` and bound.
:param name: Pointer to the structure to be filled with the address data.
In order to support IPv4 and IPv6 `struct sockaddr_storage` should be
used.
:param namelen: On input it indicates the data of the `name` field. On
output it indicates how much of it was filled.
:returns: 0 on success, or an error code < 0 on failure
.. versionadded:: 1.27.0
.. c:function:: int uv_udp_getsockname(const uv_udp_t* handle, struct sockaddr* name, int* namelen)
Get the local IP and port of the UDP handle.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init` and bound.
:param name: Pointer to the structure to be filled with the address data.
In order to support IPv4 and IPv6 `struct sockaddr_storage` should be
used.
:param namelen: On input it indicates the data of the `name` field. On
output it indicates how much of it was filled.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_set_membership(uv_udp_t* handle, const char* multicast_addr, const char* interface_addr, uv_membership membership)
Set membership for a multicast address
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param multicast_addr: Multicast address to set membership for.
:param interface_addr: Interface address.
:param membership: Should be ``UV_JOIN_GROUP`` or ``UV_LEAVE_GROUP``.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_set_source_membership(uv_udp_t* handle, const char* multicast_addr, const char* interface_addr, const char* source_addr, uv_membership membership)
Set membership for a source-specific multicast group.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param multicast_addr: Multicast address to set membership for.
:param interface_addr: Interface address.
:param source_addr: Source address.
:param membership: Should be ``UV_JOIN_GROUP`` or ``UV_LEAVE_GROUP``.
:returns: 0 on success, or an error code < 0 on failure.
.. versionadded:: 1.32.0
.. c:function:: int uv_udp_set_multicast_loop(uv_udp_t* handle, int on)
Set IP multicast loop flag. Makes multicast packets loop back to
local sockets.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param on: 1 for on, 0 for off.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_set_multicast_ttl(uv_udp_t* handle, int ttl)
Set the multicast ttl.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param ttl: 1 through 255.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_set_multicast_interface(uv_udp_t* handle, const char* interface_addr)
Set the multicast interface to send or receive data on.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param interface_addr: interface address.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_set_broadcast(uv_udp_t* handle, int on)
Set broadcast on or off.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param on: 1 for on, 0 for off.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_set_ttl(uv_udp_t* handle, int ttl)
Set the time to live.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param ttl: 1 through 255.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: int uv_udp_send(uv_udp_send_t* req, uv_udp_t* handle, const uv_buf_t bufs[], unsigned int nbufs, const struct sockaddr* addr, uv_udp_send_cb send_cb)
Send data over the UDP socket. If the socket has not previously been bound
with :c:func:`uv_udp_bind` it will be bound to 0.0.0.0
(the "all interfaces" IPv4 address) and a random port number.
On Windows if the `addr` is initialized to point to an unspecified address
(``0.0.0.0`` or ``::``) it will be changed to point to ``localhost``.
This is done to match the behavior of Linux systems.
For connected UDP handles, `addr` must be set to `NULL`, otherwise it will
return `UV_EISCONN` error.
For connectionless UDP handles, `addr` cannot be `NULL`, otherwise it will
return `UV_EDESTADDRREQ` error.
:param req: UDP request handle. Need not be initialized.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param bufs: List of buffers to send.
:param nbufs: Number of buffers in `bufs`.
:param addr: `struct sockaddr_in` or `struct sockaddr_in6` with the
address and port of the remote peer.
:param send_cb: Callback to invoke when the data has been sent out.
:returns: 0 on success, or an error code < 0 on failure.
.. versionchanged:: 1.19.0 added ``0.0.0.0`` and ``::`` to ``localhost``
mapping
.. versionchanged:: 1.27.0 added support for connected sockets
.. c:function:: int uv_udp_try_send(uv_udp_t* handle, const uv_buf_t bufs[], unsigned int nbufs, const struct sockaddr* addr)
Same as :c:func:`uv_udp_send`, but won't queue a send request if it can't
be completed immediately.
For connected UDP handles, `addr` must be set to `NULL`, otherwise it will
return `UV_EISCONN` error.
For connectionless UDP handles, `addr` cannot be `NULL`, otherwise it will
return `UV_EDESTADDRREQ` error.
:returns: >= 0: number of bytes sent (it matches the given buffer size).
< 0: negative error code (``UV_EAGAIN`` is returned when the message
can't be sent immediately).
.. versionchanged:: 1.27.0 added support for connected sockets
.. c:function:: int uv_udp_recv_start(uv_udp_t* handle, uv_alloc_cb alloc_cb, uv_udp_recv_cb recv_cb)
Prepare for receiving data. If the socket has not previously been bound
with :c:func:`uv_udp_bind` it is bound to 0.0.0.0 (the "all interfaces"
IPv4 address) and a random port number.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:param alloc_cb: Callback to invoke when temporary storage is needed.
:param recv_cb: Callback to invoke with received data.
:returns: 0 on success, or an error code < 0 on failure.
.. note::
When using :man:`recvmmsg(2)`, the number of messages received at a time is limited
by the number of max size dgrams that will fit into the buffer allocated in `alloc_cb`, and
`suggested_size` in `alloc_cb` for udp_recv is always set to the size of 1 max size dgram.
.. versionchanged:: 1.35.0 added support for :man:`recvmmsg(2)` on supported platforms).
The use of this feature requires a buffer larger than
2 * 64KB to be passed to `alloc_cb`.
.. versionchanged:: 1.37.0 :man:`recvmmsg(2)` support is no longer enabled implicitly,
it must be explicitly requested by passing the `UV_UDP_RECVMMSG` flag to
:c:func:`uv_udp_init_ex`.
.. versionchanged:: 1.39.0 :c:func:`uv_udp_using_recvmmsg` can be used in `alloc_cb` to
determine if a buffer sized for use with :man:`recvmmsg(2)` should be
allocated for the current handle/platform.
.. c:function:: int uv_udp_using_recvmmsg(uv_udp_t* handle)
Returns 1 if the UDP handle was created with the `UV_UDP_RECVMMSG` flag
and the platform supports :man:`recvmmsg(2)`, 0 otherwise.
.. versionadded:: 1.39.0
.. c:function:: int uv_udp_recv_stop(uv_udp_t* handle)
Stop listening for incoming datagrams.
:param handle: UDP handle. Should have been initialized with
:c:func:`uv_udp_init`.
:returns: 0 on success, or an error code < 0 on failure.
.. c:function:: size_t uv_udp_get_send_queue_size(const uv_udp_t* handle)
Returns `handle->send_queue_size`.
.. versionadded:: 1.19.0
.. c:function:: size_t uv_udp_get_send_queue_count(const uv_udp_t* handle)
Returns `handle->send_queue_count`.
.. versionadded:: 1.19.0
.. seealso:: The :c:type:`uv_handle_t` API functions also apply.
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