I am having a problem writing a TCP socket message using boost:asio async_* I am new to using boost asio sockets. reading what I could find (this list, samples, other forums) I have added boost::asio socket use to my application. What works is: accept, receive, parse and reply to a message. After my client sends a message and receives a response it remains connected and starts an async receive. Several seconds later my server tries to send another message to the client (by calling server::write()). the code runs ok up to connection::handle_writeMessage() where error is: 2719 “The file handle supplied is not valid”. I thought I read (links below) that using strand::wrap() to queue the async_* calls and io_service::post() to post the initial function call would allow a thread that didn’t call io_service::run() to initiate the sending or a message. http://stackoverflow.com/questions/4078484/using-boost-sockets-do-i-need-onl... http://stackoverflow.com/questions/4090567/better-understanding-boosts-chat-... http://groups.google.com/group/boost-list/browse_thread/thread/124a643a06d67... did I interpret this incorrectly? Did I code it wrong? Thank you for your time and advice. to develop my code I started with the http3 and chat server samples. Changes include: - server::threads is a class member - server::run() returns without waiting for threads to stop so I start other threads in my program - added server::stop() to stop threads. - server::write() is called from another thread. - connection::do_writeMessage() and connection::handle_writeMessage() are from the chat server sample. A summary of my server code is below. its long, but should be familiar from the samples. Server.hpp std::vector<boost::shared_ptr<boost::thread> > threads; server::server : thread_pool_size_(2), // 1 thread for wait, read, reply. 1 for unsolicited writes. acceptor_(io_service_), new_connection_(new connection(io_service_, request_handler_)), request_handler_() { async_accept(new_connection_->socket(), boost::bind(&server::handle_accept, this, boost::asio::placeholders::error)); } void server::run() { // 1 thread for wait, read, reply. 1 for unsolicited writes. // Create a pool of threads to run all of the io_services. //std::vector<boost::shared_ptr<boost::thread> > threads; for (std::size_t i = 0; i < thread_pool_size_; ++i) { boost::shared_ptr<boost::thread> thread(new boost::thread( boost::bind(&boost::asio::io_service::run, &io_service_))); threads.push_back(thread); } } void server::stop() { io_service_.stop(); // Wait for all threads in the pool to exit. for (std::size_t i = 0; i < threads.size(); ++i) { threads[i]->join(); } } server::handle_accept (const boost::system::error_code& e) { if (!e) { // read, parse and reply new_connection_->start(); new_connection_.reset(new connection(io_service_, request_handler_)); // ready to accept another connection cout << "waiting for new accept ..." << endl; acceptor_.async_accept(new_connection_->socket(), boost::bind(&server::handle_accept, this, boost::asio::placeholders::error)); } } // public // called from another thread in my program to send an unsolicited message to my connected client void server::write(const string& msg) { io_service_.post(boost::bind(&connection::do_writeMessage, new_connection_, msg)); } - - - - - - - - - - connection::connection(boost::asio::io_service& io_service, request_handler& handler) : strand_(io_service), socket_(io_service), request_handler_(handler) { _running = true; } void connection::start() { buffer_.fill (0); socket_.async_read_some(boost::asio::buffer(buffer_), strand_.wrap( boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred) ) ); } void connection::handle_read(const boost::system::error_code& e, std::size_t bytes_transferred) { if (!e) { // parse what we have so far. request_parser_.parse() is my code and it works correctly. // when successful result==true, request boost::tribool result; request_.reset(); boost::tie(result, boost::tuples::ignore) = request_parser_.parse( request_, buffer_.data(), buffer_.data() + bytes_transferred); if (result) { // we read an entire message // this is my code to process the message and put fill in the reply_ buffer. request_handler_.handle_request(request_, reply_); // send the reply boost::asio::async_write(socket_, reply_.to_buffers(), strand_.wrap( boost::bind(&connection::handle_writeResponse, shared_from_this(), boost::asio::placeholders::error) ) ); } else if (!result) { // there was an error reading the message boost::asio::async_write(socket_, reply_.to_buffers(), strand_.wrap( boost::bind(&connection::handle_writeResponse, shared_from_this(), boost::asio::placeholders::error) ) ); } else { // read some ok. need to read some more. socket_.async_read_some(boost::asio::buffer(buffer_), strand_.wrap( boost::bind(&connection::handle_read, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred) ) ); } } else { cout << "connection::handle_read: error: " << e.value() << " " << e.message() << endl; } // If an error occurs then no new asynchronous operations are started. This // means that all shared_ptr references to the connection object will // disappear and the object will be destroyed automatically after this // handler returns. The connection class's destructor closes the socket. } void connection::handle_writeResponse(const boost::system::error_code& e) { if (!e) { // test. This message is received by my client. do_writeMessage ("hello world"); // ready to read more start(); } else { cout << "connection::handle_writeMessage: error sending to client: " << e.value() << " " << e.message() << endl; } // No new asynchronous operations are started. This means that all shared_ptr // references to the connection object will disappear and the object will be // destroyed automatically after this handler returns. The connection class's // destructor closes the socket. } - - - - - - - - - - // call to this function is posed to io_service from server::write // public void connection::do_writeMessage(string msg) { bool write_in_progress = !_messagesToWrite.empty(); _messagesToWrite.push_back(msg); // if there are any in the queue, handle_writeMessage is already sending them. if (write_in_progress) { cout << "connection::do_writeMessage: write in progress." << endl; } else { // start the async write. boost::asio::async_write(socket_, boost::asio::buffer(_messagesToWrite.front().data(), _messagesToWrite.front().length()), strand_.wrap( boost::bind(&connection::handle_writeMessage, shared_from_this()/*this*/, boost::asio::placeholders::error) ) ); } } // async write is done. if no error and more messages to write, write them, too. void connection::handle_writeMessage(const boost::system::error_code& error) { if (!error) { cout << "connection::handle_writeMessage: message written ok." << endl; // remove the message we just wrote _messagesToWrite.pop_front(); // any more? if (!_messagesToWrite.empty()) { // write the next one and call this function when that'd done. boost::asio::async_write(socket_, boost::asio::buffer(_messagesToWrite.front().data(), _messagesToWrite.front().length()), strand_.wrap( boost::bind(&connection::handle_writeMessage, shared_from_this()/*this*/, boost::asio::placeholders::error) ) ); } else { cout << "connection::handle_writeMessage: no more messages" << endl; } } else { cout << "connection::handle_writeMessage: error: " << error.value() << " " << error.message() << endl; } // let this async chain end. } - - - - - - - - - - main() { pTCPServer = new http::server3::server (argv[TCPPortNumber]); if (pTCPServer) { pTCPServer->run(); } // start thread that will initiate 2nd message … … … }