How can I pass the source IP in a UDP server using Boost ASIO

Question

I need to get the source IP for a datagram in a UDP server I'm writing using boost ASIO. In the example udp datagram server the line:

Note: my current code is identical to the existing udp async server example in the boost asio documentation.

 socket_.async_receive_from(
        boost::asio::buffer(data_, max_length), sender_endpoint_,
        boost::bind(&server::handle_receive_from, this,
          boost::asio::placeholders::error,
          boost::asio::placeholders::bytes_transferred));

Is passing error and bytes_transferred. I also need the address of the message.

Now I know I can use sender_endpoint_.address().to_string() directly, but I I would like to pass this in as a parameter.

So I tried placing sender_endpoint_.address() in as a parameter. i.e.

socket_.async_receive_from(
        boost::asio::buffer(data_, MAX_LENGTH), sender_endpoint_,
        boost::bind(&server::handle_receive_from, this,
          boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred,
                    sender_endpoint_.address()));

But the result is 0.0.0.0 when read from handle_receive_from. However, if I simply access the sender_endpoint_.address() inside handle_receive_from I get 127.0.0.1 which is correct.

How do pass this correctly? I need this because there are going to be multiple threads calling io_service.run() so a packet from another source may overwrite sender_endpoint and I need to be able to reply to that source packet.