asio C++ library

basic_datagram_socket::async_send_to (1 of 2 overloads)

Start an asynchronous send.

    typename ConstBufferSequence,
    typename WriteHandler = DEFAULT>
DEDUCED async_send_to(
    const ConstBufferSequence & buffers,
    const endpoint_type & destination,
    WriteHandler && handler = DEFAULT);

This function is used to asynchronously send a datagram to the specified remote endpoint. The function call always returns immediately.



One or more data buffers to be sent to the remote endpoint. Although the buffers 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 handler is called.


The remote endpoint to which the data will be sent. Copies will be made of the endpoint as required.


The handler to be called when the send operation completes. Copies will be made of the handler as required. The function signature of the handler must be:

void handler(
  const asio::error_code& error, // Result of operation.
  std::size_t bytes_transferred           // Number of bytes sent.

Regardless of whether the asynchronous operation completes immediately or not, the 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 post.


To send a single data buffer use the buffer function as follows:

asio::ip::udp::endpoint destination(
    asio::ip::address::from_string(""), 12345);
    asio::buffer(data, size), destination, handler);

See the buffer documentation for information on sending multiple buffers in one go, and how to use it with arrays, boost::array or std::vector.

Per-Operation Cancellation

On POSIX or Windows operating systems, this asynchronous operation supports cancellation for the following cancellation_type values: