![]() |
Home | Libraries | People | FAQ | More |
int main()
{
try
{
Create a server object to accept incoming client requests, and run the io_context object.
boost::asio::io_context io_context;
udp_server server(io_context);
io_context.run();
}
catch (std::exception& e)
{
std::cerr << e.what() << std::endl;
}
return 0;
}
class udp_server
{
public:
The constructor initialises a socket to listen on UDP port 13.
udp_server(boost::asio::io_context& io_context)
: socket_(io_context, udp::endpoint(udp::v4(), 13))
{
start_receive();
}
private:
void start_receive()
{
The function ip::udp::socket::async_receive_from()
will cause the application to listen in the background for a new request.
When such a request is received, the io_context
object will invoke the handle_receive() function with two arguments:
a value of type boost::system::error_code indicating whether the operation
succeeded or failed, and a size_t value bytes_transferred
specifying the number of bytes received.
socket_.async_receive_from(
boost::asio::buffer(recv_buffer_), remote_endpoint_,
boost::bind(&udp_server::handle_receive, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
The function handle_receive() will service the client request.
void handle_receive(const boost::system::error_code& error,
std::size_t /*bytes_transferred*/)
{
The error parameter contains the result of the asynchronous
operation. Since we only provide the 1-byte recv_buffer_ to
contain the client's request, the io_context
object would return an error if the client sent anything larger. We can ignore
such an error if it comes up.
if (!error)
{
Determine what we are going to send.
boost::shared_ptr<std::string> message(
new std::string(make_daytime_string()));
We now call ip::udp::socket::async_send_to() to serve the data to the client.
socket_.async_send_to(boost::asio::buffer(*message), remote_endpoint_,
boost::bind(&udp_server::handle_send, this, message,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
When initiating the asynchronous operation, and if using boost::bind(), you must specify only the arguments that match the handler's parameter list. In this program, both of the argument placeholders (boost::asio::placeholders::error and boost::asio::placeholders::bytes_transferred) could potentially have been removed.
Start listening for the next client request.
start_receive();
Any further actions for this client request are now the responsibility of
handle_send().
} }
The function handle_send() is invoked after the service request
has been completed.
void handle_send(boost::shared_ptr<std::string> /*message*/,
const boost::system::error_code& /*error*/,
std::size_t /*bytes_transferred*/)
{
}
udp::socket socket_;
udp::endpoint remote_endpoint_;
boost::array<char, 1> recv_buffer_;
};
See the full source listing
Return to the tutorial index