.. _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 supressing 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.