Accept connections

Server needs to accept clients’ connections. First server creates an acceptor: 

  1. ......
  2. boost::asio::io_context io_context;
  3.     boost::asio::ip::tcp::acceptor acceptor{
  4.         io_context,
  5.         boost::asio::ip::tcp::endpoint{boost::asio::ip::tcp::v6(), 3303}};
  6. ......

boost::asio::ip::tcp::acceptor is an instance of basic_socket_acceptor: 

  1. class tcp
  2. {
  3. ......
  4.   /// The TCP acceptor type.
  5.   typedef basic_socket_acceptor<tcp> acceptor;
  6. ......
  7. }

The following constructor of basic_socket_acceptor combines creating socket, setting reuse address, binding & listening functions: 

  1. basic_socket_acceptor(boost::asio::io_context& io_context,
  2.     const endpoint_type& endpoint, bool reuse_addr = true)
  3.   : basic_io_object<BOOST_ASIO_SVC_T>(io_context)
  4. {
  5. ......
  6. }

Then acceptor will accept the clients’ connections. Following simple example just shows client’s address and close the connection: 

  1. #include <boost/asio.hpp>
  2. #include <iostream>
  4. int main()
  5. {
  6.     try
  7.     {
  8.         boost::asio::io_context io_context;
  9.         boost::asio::ip::tcp::acceptor acceptor{
  10.             io_context,
  11.             boost::asio::ip::tcp::endpoint{boost::asio::ip::tcp::v6(), 3303}};
  13.         while (1)
  14.         {
  15.             boost::asio::ip::tcp::socket socket{io_context};
  16.             acceptor.accept(socket);
  18.             std::cout << socket.remote_endpoint() << " connects to " << socket.local_endpoint() << '\n';
  19.         }
  20.     }
  21.     catch (std::exception& e)
  22.     {
  23.         std::cerr << e.what() << '\n';
  24.         return -1;
  25.     }
  27.     return 0;
  28. }

The running result is like this: 

  1. [::ffff:10.217.242.61]:39290 connects to [::ffff:192.168.35.145]:3303
  2. ......