async_read_until: insufficient buffer space or queue is full

Question

I'm converting an application from using Juce asynchronous i/o to asio. The first part is to rewrite the code that receives traffic from another application on the same machine (it's a Lightroom Lua plugin that sends \\n delimited messages on port 58764). Whenever I successfully connect to that port with my C++ program, I get a series of error codes, all the same:

An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full.

Can someone point out my error? I can see that the socket is successfully opened. I've reduced this from my full program to a minimal example. I also tried it with connect instead of async_connect and had the same problem.

#include <iostream>
#include "asio.hpp"

asio::io_context io_context_;
asio::ip::tcp::socket socket_{io_context_};

void loop_me()
{
   asio::streambuf streambuf{};
   while (true) {
      if (!socket_.is_open()) {
         return;
      }
      else {
         asio::async_read_until(socket_, streambuf, '\n',
             [&streambuf](const asio::error_code& error_code, std::size_t bytes_transferred) {
                if (error_code) {
                   std::cerr << "Socket error " << error_code.message() << std::endl;
                   return;
                }
                // Extract up to the first delimiter.
                std::string command{buffers_begin(streambuf.data()),
                    buffers_begin(streambuf.data()) + bytes_transferred};
                std::cout << command << std::endl;
                streambuf.consume(bytes_transferred);
             });

      }
   }
}

int main()
{
   auto work_{asio::make_work_guard(io_context_)};
   std::thread io_thread_;
   std::thread run_thread_;
   io_thread_ = std::thread([] { io_context_.run(); });
   socket_.async_connect(asio::ip::tcp::endpoint(asio::ip::address_v4::loopback(), 58764),
       [&run_thread_](const asio::error_code& error) {
          if (!error) {
             std::cout << "Socket connected in LR_IPC_In\n";
             run_thread_ = std::thread(loop_me);
          }
          else {
             std::cerr << "LR_IPC_In socket connect failed " << error.message() << std::endl;
          }
       });
   std::this_thread::sleep_for(std::chrono::seconds(1));
   socket_.close();
   io_context_.stop();
   if (io_thread_.joinable())
      io_thread_.join();
   if (run_thread_.joinable())
      run_thread_.join();
}

Answer 1

You are trying to start an infinite number of asynchronous read operations at the same time. You shouldn't start a new asynchronous read until the previous one finished.

async_read_until returns immediately, even though the data hasn't been received yet. That's the point of "async".