HI Andreas, you are right. this is not crash. It is an exception. I did the following small code to explain the issue better ============================================ #include <iostream> #include <boost/asio/ip/tcp.hpp> #include <boost/lexical_cast.hpp> using namespace boost::asio; int main(int argc, char* argv[]) { io_service ios; try { int i; for (i=0;i<1000;i++) { int m_port = 80; std::string m_host = "www.yahoo.com"; boost::system::error_code ec; boost::asio::ip::tcp::resolver resolver( ios ); boost::asio::ip::tcp::resolver::query query( m_host, boost::lexical_cast< std::string >( m_port )); boost::asio::ip::tcp::resolver::iterator endpointIterator = resolver.resolve( query ); for(;endpointIterator != ip::tcp::resolver_iterator(); ++endpointIterator) { std::cout << "i: " << i << " ip: " << endpointIterator->endpoint().address().to_string() << std::endl; } } } catch(std::exception const& ex) { std::cerr << "Error: " << ex.what() << '\n'; } } ============================================= the output goes fine but around 300, it throws the exception. i: 327 ip: 98.139.183.24 i: 328 ip: 98.139.183.24 i: 329 ip: 98.139.183.24 Error: Host not found (authoritative) ============================================ you are suggesting to handle the exception which I will do. But i wonder why this is not happening in windows but ubuntu? I wonder if my ubuntu is missing some configuration. I did install Miredo for Ipv6 but it did not help. i feel like this is something to do with network settings issue, NAT issue or something.... Thank you for the suggestion. mustafa -- View this message in context: http://boost.2283326.n4.nabble.com/boost-asio-ip-tcp-resolver-query-does-not... Sent from the Boost - Users mailing list archive at Nabble.com.