interface udp {
	use wasi:poll/poll.{pollable}
	use network.{network, error-code, ip-socket-address, ip-address-family}


	/// A UDP socket handle.
	type udp-socket = u32


	record datagram {
		data: list<u8>, // Theoretical max size: ~64 KiB. In practice, typically less than 1500 bytes.
		remote-address: ip-socket-address,

		/// Possible future additions:
		/// local-address: ip-socket-address, // IP_PKTINFO / IP_RECVDSTADDR / IPV6_PKTINFO
		/// local-interface: u32, // IP_PKTINFO / IP_RECVIF
		/// ttl: u8, // IP_RECVTTL
		/// dscp: u6, // IP_RECVTOS
		/// ecn: u2, // IP_RECVTOS
	}



	/// Bind the socket to a specific network on the provided IP address and port.
	///
	/// If the IP address is zero (`0.0.0.0` in IPv4, `::` in IPv6), it is left to the implementation to decide which
	/// network interface(s) to bind to.
	/// If the TCP/UDP port is zero, the socket will be bound to a random free port.
	/// 
	/// When a socket is not explicitly bound, the first invocation to connect will implicitly bind the socket.
	/// 
	/// Unlike in POSIX, this function is async. This enables interactive WASI hosts to inject permission prompts.
	/// 
	/// # Typical `start` errors
	/// - `address-family-mismatch`:   The `local-address` has the wrong address family. (EINVAL)
	/// - `already-bound`:             The socket is already bound. (EINVAL)
	/// - `concurrency-conflict`:      Another `bind` or `connect` operation is already in progress. (EALREADY)
	/// 
	/// # Typical `finish` errors
	/// - `ephemeral-ports-exhausted`: No ephemeral ports available. (EADDRINUSE, ENOBUFS on Windows)
	/// - `address-in-use`:            Address is already in use. (EADDRINUSE)
	/// - `address-not-bindable`:      `local-address` is not an address that the `network` can bind to. (EADDRNOTAVAIL)
	/// - `not-in-progress`:           A `bind` operation is not in progress.
	/// - `would-block`:               Can't finish the operation, it is still in progress. (EWOULDBLOCK, EAGAIN)
	/// 
	/// # References
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/bind.html>
	/// - <https://man7.org/linux/man-pages/man2/bind.2.html>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-bind>
	/// - <https://man.freebsd.org/cgi/man.cgi?query=bind&sektion=2&format=html>
	start-bind: func(this: udp-socket, network: network, local-address: ip-socket-address) -> result<_, error-code>
	finish-bind: func(this: udp-socket) -> result<_, error-code>

	/// Set the destination address.
	/// 
	/// The local-address is updated based on the best network path to `remote-address`.
	/// 
	/// When a destination address is set:
	/// - all receive operations will only return datagrams sent from the provided `remote-address`.
	/// - the `send` function can only be used to send to this destination.
	/// 
	/// Note that this function does not generate any network traffic and the peer is not aware of this "connection".
	/// 
	/// Unlike in POSIX, this function is async. This enables interactive WASI hosts to inject permission prompts.
	/// 
	/// # Typical `start` errors
	/// - `address-family-mismatch`:   The `remote-address` has the wrong address family. (EAFNOSUPPORT)
	/// - `invalid-remote-address`:    The IP address in `remote-address` is set to INADDR_ANY (`0.0.0.0` / `::`). (EDESTADDRREQ, EADDRNOTAVAIL)
	/// - `invalid-remote-address`:    The port in `remote-address` is set to 0. (EDESTADDRREQ, EADDRNOTAVAIL)
	/// - `already-attached`:          The socket is already bound to a different network. The `network` passed to `connect` must be identical to the one passed to `bind`.
	/// - `concurrency-conflict`:      Another `bind` or `connect` operation is already in progress. (EALREADY)
	/// 
	/// # Typical `finish` errors
	/// - `ephemeral-ports-exhausted`: Tried to perform an implicit bind, but there were no ephemeral ports available. (EADDRINUSE, EADDRNOTAVAIL on Linux, EAGAIN on BSD)
	/// - `not-in-progress`:           A `connect` operation is not in progress.
	/// - `would-block`:               Can't finish the operation, it is still in progress. (EWOULDBLOCK, EAGAIN)
	/// 
	/// # References
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/connect.html>
	/// - <https://man7.org/linux/man-pages/man2/connect.2.html>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-connect>
	/// - <https://man.freebsd.org/cgi/man.cgi?connect>
	start-connect: func(this: udp-socket, network: network, remote-address: ip-socket-address) -> result<_, error-code>
	finish-connect: func(this: udp-socket) -> result<_, error-code>

	/// Receive messages on the socket.
	/// 
	/// This function attempts to receive up to `max-results` datagrams on the socket without blocking.
	/// The returned list may contain fewer elements than requested, but never more.
	/// If `max-results` is 0, this function returns successfully with an empty list.
	/// 
	/// # Typical errors
	/// - `not-bound`:          The socket is not bound to any local address. (EINVAL)
	/// - `remote-unreachable`: The remote address is not reachable. (ECONNREFUSED, ECONNRESET, ENETRESET on Windows, EHOSTUNREACH, EHOSTDOWN, ENETUNREACH, ENETDOWN)
	/// - `would-block`:        There is no pending data available to be read at the moment. (EWOULDBLOCK, EAGAIN)
	/// 
	/// # References
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/recvfrom.html>
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/recvmsg.html>
	/// - <https://man7.org/linux/man-pages/man2/recv.2.html>
	/// - <https://man7.org/linux/man-pages/man2/recvmmsg.2.html>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-recv>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-recvfrom>
	/// - <https://learn.microsoft.com/en-us/previous-versions/windows/desktop/legacy/ms741687(v=vs.85)>
	/// - <https://man.freebsd.org/cgi/man.cgi?query=recv&sektion=2>
	receive: func(this: udp-socket, max-results: u64) -> result<list<datagram>, error-code>

	/// Send messages on the socket.
	/// 
	/// This function attempts to send all provided `datagrams` on the socket without blocking and
	/// returns how many messages were actually sent (or queued for sending).
	/// 
	/// This function semantically behaves the same as iterating the `datagrams` list and sequentially
	/// sending each individual datagram until either the end of the list has been reached or the first error occurred.
	/// If at least one datagram has been sent successfully, this function never returns an error.
	/// 
	/// If the input list is empty, the function returns `ok(0)`.
	/// 
	/// The remote address option is required. To send a message to the "connected" peer,
	/// call `remote-address` to get their address.
	/// 
	/// # Typical errors
	/// - `address-family-mismatch`: The `remote-address` has the wrong address family. (EAFNOSUPPORT)
	/// - `invalid-remote-address`:  The IP address in `remote-address` is set to INADDR_ANY (`0.0.0.0` / `::`). (EDESTADDRREQ, EADDRNOTAVAIL)
	/// - `invalid-remote-address`:  The port in `remote-address` is set to 0. (EDESTADDRREQ, EADDRNOTAVAIL)
	/// - `already-connected`:       The socket is in "connected" mode and the `datagram.remote-address` does not match the address passed to `connect`. (EISCONN)
	/// - `not-bound`:               The socket is not bound to any local address. Unlike POSIX, this function does not perform an implicit bind.
	/// - `remote-unreachable`:      The remote address is not reachable. (ECONNREFUSED, ECONNRESET, ENETRESET on Windows, EHOSTUNREACH, EHOSTDOWN, ENETUNREACH, ENETDOWN)
	/// - `datagram-too-large`:      The datagram is too large. (EMSGSIZE)
	/// - `would-block`:             The send buffer is currently full. (EWOULDBLOCK, EAGAIN)
	/// 
	/// # References
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendto.html>
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html>
	/// - <https://man7.org/linux/man-pages/man2/send.2.html>
	/// - <https://man7.org/linux/man-pages/man2/sendmmsg.2.html>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-send>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-sendto>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsasendmsg>
	/// - <https://man.freebsd.org/cgi/man.cgi?query=send&sektion=2>
	send: func(this: udp-socket, datagrams: list<datagram>) -> result<u64, error-code>

	/// Get the current bound address.
	/// 
	/// # Typical errors
	/// - `not-bound`: The socket is not bound to any local address.
	/// 
	/// # References
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/getsockname.html>
	/// - <https://man7.org/linux/man-pages/man2/getsockname.2.html>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-getsockname>
	/// - <https://man.freebsd.org/cgi/man.cgi?getsockname>
	local-address: func(this: udp-socket) -> result<ip-socket-address, error-code>

	/// Get the address set with `connect`.
	/// 
	/// # Typical errors
	/// - `not-connected`: The socket is not connected to a remote address. (ENOTCONN)
	/// 
	/// # References
	/// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/getpeername.html>
	/// - <https://man7.org/linux/man-pages/man2/getpeername.2.html>
	/// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-getpeername>
	/// - <https://man.freebsd.org/cgi/man.cgi?query=getpeername&sektion=2&n=1>
	remote-address: func(this: udp-socket) -> result<ip-socket-address, error-code>

	/// Whether this is a IPv4 or IPv6 socket.
	/// 
	/// Equivalent to the SO_DOMAIN socket option.
	address-family: func(this: udp-socket) -> ip-address-family

	/// Whether IPv4 compatibility (dual-stack) mode is disabled or not.
	/// 
	/// Equivalent to the IPV6_V6ONLY socket option.
	/// 
	/// # Typical errors
	/// - `ipv6-only-operation`:  (get/set) `this` socket is an IPv4 socket.
	/// - `already-bound`:        (set) The socket is already bound.
	/// - `not-supported`:        (set) Host does not support dual-stack sockets. (Implementations are not required to.)
	/// - `concurrency-conflict`: (set) Another `bind` or `connect` operation is already in progress. (EALREADY)
	ipv6-only: func(this: udp-socket) -> result<bool, error-code>
	set-ipv6-only: func(this: udp-socket, value: bool) -> result<_, error-code>

	/// Equivalent to the IP_TTL & IPV6_UNICAST_HOPS socket options.
	/// 
	/// # Typical errors
	/// - `concurrency-conflict`: (set) Another `bind` or `connect` operation is already in progress. (EALREADY)
	unicast-hop-limit: func(this: udp-socket) -> result<u8, error-code>
	set-unicast-hop-limit: func(this: udp-socket, value: u8) -> result<_, error-code>

	/// The kernel buffer space reserved for sends/receives on this socket.
	/// 
	/// Note #1: an implementation may choose to cap or round the buffer size when setting the value.
	/// 	In other words, after setting a value, reading the same setting back may return a different value.
	/// 
	/// Note #2: there is not necessarily a direct relationship between the kernel buffer size and the bytes of
	/// 	actual data to be sent/received by the application, because the kernel might also use the buffer space
	/// 	for internal metadata structures.
	/// 
	/// Equivalent to the SO_RCVBUF and SO_SNDBUF socket options.
	/// 
	/// # Typical errors
	/// - `concurrency-conflict`: (set) Another `bind` or `connect` operation is already in progress. (EALREADY)
	receive-buffer-size: func(this: udp-socket) -> result<u64, error-code>
	set-receive-buffer-size: func(this: udp-socket, value: u64) -> result<_, error-code>
	send-buffer-size: func(this: udp-socket) -> result<u64, error-code>
	set-send-buffer-size: func(this: udp-socket, value: u64) -> result<_, error-code>

	/// Create a `pollable` which will resolve once the socket is ready for I/O.
	/// 
	/// Note: this function is here for WASI Preview2 only.
	/// It's planned to be removed when `future` is natively supported in Preview3.
	subscribe: func(this: udp-socket) -> pollable

	/// Dispose of the specified `udp-socket`, after which it may no longer be used.
	/// 
	/// Note: this function is scheduled to be removed when Resources are natively supported in Wit.
	drop-udp-socket: func(this: udp-socket)
}