Handling "reset by peer" scenario with boost::asio - c++

Question

I have a server method that waits for new incoming TCP connections, for each connection I'm creating two threads (detached) for handling various tasks.
void MyClass::startServer(boost::asio::io_service& io_service, unsigned short port) {
tcp::acceptor TCPAcceptor(io_service, tcp::endpoint(tcp::v4(), port));
bool UARTToWiFiGatewayStarted = false;
for (;;) {
auto socket(std::shared_ptr<tcp::socket>(new tcp::socket(io_service)));
/*!
* Accept a new connected WiFi client.
*/
TCPAcceptor.accept(*socket);
socket->set_option( tcp::no_delay( true ) );
MyClass::enableCommunicationSession();
// start one worker thread.
std::thread(WiFiToUARTWorkerSession, socket, this->LINport, this->LINbaud).detach();
// only if this is the first connected client:
if(false == UARTToWiFiGatewayStarted) {
std::thread(UARTToWifiWorkerSession, socket, this->UARTport, this->UARTbaud).detach();
UARTToWiFiGatewayStarted = true;
}
}
}
This works fine for starting the communication, but the problem appears when the client disconnects and connects again (or at least tries to connect again).
When the current client disconnects, I stop the communication (by stopping the internal infinite loops from both functions, then they'll return).
void Gateway::WiFiToUARTWorkerSession(std::shared_ptr<tcp::socket> socket, ...) {
/*!
* various code here...
*/
try {
while(true == MyClass::communicationSessionStatus) {
/*!
* Buffer used for storing the UART-incoming data.
*/
unsigned char WiFiDataBuffer[max_incoming_wifi_data_length];
boost::system::error_code error;
/*!
* Read the WiFi-available data.
*/
size_t length = socket->read_some(boost::asio::buffer(WiFiDataBuffer), error);
/*!
* Handle possible read errors.
*/
if (error == boost::asio::error::eof) {
break; // Connection closed cleanly by peer.
}
else if (error) {
// this will cause the infinite loops from the both worker functions to stop, and when they stop the functions will return.
MyClass::disableCommunicationSession();
sleep(1);
throw boost::system::system_error(error); // Some other error.
}
uart->write(WiFiDataBuffer, length);
}
}
catch (std::exception &exception) {
std::cerr << "[APP::exception] Exception in thread: " << exception.what() << std::endl;
}
}
I expect that when I reconnect the communication should work again (the MyClass::startServer(...) will create and detach again two worker threads that will do the same things.
The problem is that when I connect the second time I get:
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error> >'
what(): write: Broken pipe
From what I found about this error it seems that the server (this application) sends something via TCP to a client that was disconnected.
What I'm doing wrong?
How can I solve this problem?

Answer 1

A read of length 0 with no error is also an indication of eof. The boost::asio::error::eof error code is normally more useful when you're checking the result of a composed operation.
When this error condition is missed, the code as presented will call write on a socket which has now been shutdown. You have used the form of write which does not take a reference to an error_code. This form will throw if there is an error. There will be an error. The read has failed.