...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
This tutorial program shows how to use asio to implement a server application with TCP.
#include <ctime> #include <iostream> #include <string> #include <boost/asio.hpp> using boost::asio::ip::tcp;
We define the function make_daytime_string()
to create the string
to be sent back to the client. This function will be reused in all of our
daytime server applications.
std::string make_daytime_string() { using namespace std; // For time_t, time and ctime; time_t now = time(0); return ctime(&now); } int main() { try { boost::asio::io_context io_context;
A ip::tcp::acceptor object needs to be created to listen for new connections. It is initialised to listen on TCP port 13, for IP version 4.
tcp::acceptor acceptor(io_context, tcp::endpoint(tcp::v4(), 13));
This is an iterative server, which means that it will handle one connection at a time. Create a socket that will represent the connection to the client, and then wait for a connection.
for (;;) { tcp::socket socket(io_context); acceptor.accept(socket);
A client is accessing our service. Determine the current time and transfer this information to the client.
std::string message = make_daytime_string(); boost::system::error_code ignored_error; boost::asio::write(socket, boost::asio::buffer(message), ignored_error); } }
Finally, handle any exceptions.
catch (std::exception& e) { std::cerr << e.what() << std::endl; } return 0; }
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