TCPEchoServer.cpp

#include <iostream>
#include <string>
#include <asio.hpp>
#include <asio/io_context.hpp>

using asio::awaitable;
using asio::co_spawn;
using asio::detached;
using asio::ip::tcp;
using asio::use_awaitable;
using asio::io_context;
using namespace std;

awaitable<void> session(tcp::socket socket)
{
   string data;
   cout << "Client connected: " << socket.remote_endpoint() << '\n';
   while (data != "quit")
   {
       data.clear();
       co_await asio::async_read_until(socket, asio::dynamic_buffer(data), '\n', use_awaitable); // line-by-line reading
       if (data != "")
           co_await asio::async_write(socket, asio::buffer(data), use_awaitable);
   }
   cout << "Client disconnected: " << socket.remote_endpoint() << '\n';
}

awaitable<void> listener(io_context& ctx, unsigned short port)
{
   tcp::acceptor acceptor(ctx, { tcp::v4(), port });
   cout << "Server listening on port " << port << "..." << endl;
   while (true)
   {
       tcp::socket socket = co_await acceptor.async_accept(use_awaitable);
       co_spawn(ctx, session(move(socket)), detached);
   }
}

int main(int argc, char* argv[])
{
   if (argc < 2)
   {
       cerr << "Usage: " << argv[0] << " <port>" << endl;
       return 1;
   }

   io_context ctx;
   string arg = argv[1];
   size_t pos;
   unsigned short port = stoi(arg, &pos);

   asio::signal_set signals(ctx, SIGINT, SIGTERM);
   signals.async_wait([&](auto, auto) { ctx.stop(); });
   auto listen = listener(ctx, port);
   co_spawn(ctx, move(listen), asio::detached);
   ctx.run();
}