A forward range of mutable buffer sequences, one per datagram, into which the data will be received. Although the range object may be copied as necessary, ownership of the underlying memory blocks is retained by the caller, which must guarantee that they remain valid until the completion handler is called.

A forward range of endpoint objects, one per datagram, that receive the endpoint of the remote sender of each datagram. Although the range object may be copied as necessary, ownership of the underlying endpoint objects is retained by the caller, which must guarantee that they remain valid until the completion handler is called.

A forward range of std::size_t, one per datagram, into which the number of bytes received in each datagram is written. Although the range object may be copied as necessary, ownership of the underlying elements is retained by the caller, which must guarantee that they remain valid until the completion handler is called.

A forward range of socket_base::message_flags, one per datagram, into which the flags associated with each received datagram are written. Although the range object may be copied as necessary, ownership of the underlying elements is retained by the caller, which must guarantee that they remain valid until the completion handler is called.

The completion token that will be used to produce a completion handler, which will be called when the receive completes. Potential completion tokens include use_future, use_awaitable, yield_context, or a function object with the correct completion signature. The function signature of the completion handler must be:

void handler(
  const boost::system::error_code& error, // Result of operation.
  std::size_t messages_transferred // Number of datagrams received.
);

Regardless of whether the asynchronous operation completes immediately or not, the completion handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using async_immediate.