boost::asio 에서 복수의 파일을 다운받게하려 하는데요

uint64_t leftSize = fileSize - outputFile.tellp();
 
if(leftSize >= buf.size())
{
	async_read(socket, 
			boost::asio::buffer(buf.c_array(), buf.size()),
			boost::bind(&tcpConnection::handleReadFileContent, 
						shared_from_this(),
						boost::asio::placeholders::error, 
						boost::asio::placeholders::bytes_transferred)
		);
}
else
{
	async_read(socket, 
			boost::asio::buffer(buf.c_array(), leftSize),
			boost::bind(&tcpConnection::handleReadFileContent, 
						shared_from_this(),
						boost::asio::placeholders::error, 
						boost::asio::placeholders::bytes_transferred)
		);
}