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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Exception in async_server_base/async_connection during port scanning (nmap)","articleBody":"When `boost::network::http::server` is listening for new connections, it sometimes throws the following exception from it's `run()` method (or `asio::io_service::run()`) when the host is being port scanned using nmap:\n\n```\nboost::exception_detail::clone_impl\u003cboost::exception_detail::error_info_injector\u003cstd::system_error\u003e\u003e\nremote_endpoint: Transport endpoint is not connected\n```\n\nAfter the exception servers stops accepting connections even if event loop is restarted and has to be `stop()`'ed and `listen()``ed again. In my tests, depending on the system, this may happen every time the host in nmap'ed or require several consequent nmaps.\n\nThis bug actually has already been reported (issue #360), but for an old version of cpp-netlib and there was no activity, so i decided to open a new issue. I am experiencing this problem with cpp-netlib 0.12.0.\n\nI have fixed the issue in my project with the following patch. I am unsure if i have fixed it the right way (for example, i might have introduced breaking API change in `stream_handler::remote_endpoint()`), but if it is ok, i can send a pull request.\n\n```\ndiff --git a/boost/network/protocol/http/server/async_connection.hpp b/boost/network/protocol/http/server/async_connection.hpp\nindex 915c6fb..eca2f68 100644\n--- a/boost/network/protocol/http/server/async_connection.hpp\n+++ b/boost/network/protocol/http/server/async_connection.hpp\n@@ -462,11 +462,18 @@ struct async_connection\n   enum state_t { method, uri, version, headers };\n\n   void start() {\n-    typename ostringstream\u003cTag\u003e::type ip_stream;\n-    ip_stream \u003c\u003c socket_.remote_endpoint().address().to_string() \u003c\u003c ':'\n-              \u003c\u003c socket_.remote_endpoint().port();\n-    request_.source = ip_stream.str();\n-    read_more(method);\n+    std::error_code ec;\n+    auto remote_endpoint = socket_.remote_endpoint(ec);\n+    \n+    if (ec) {\n+      error_encountered = in_place\u003cstd::system_error\u003e(ec);\n+    } else {\n+      typename ostringstream\u003cTag\u003e::type ip_stream;\n+      ip_stream \u003c\u003c remote_endpoint.address().to_string() \u003c\u003c ':'\n+                \u003c\u003c remote_endpoint.port();\n+      request_.source = ip_stream.str();\n+      read_more(method);\n+    }\n   }\n\n   void read_more(state_t state) {\ndiff --git a/boost/network/protocol/stream_handler.hpp b/boost/network/protocol/stream_handler.hpp\nindex 16fafc6..9d82706 100644\n--- a/boost/network/protocol/stream_handler.hpp\n+++ b/boost/network/protocol/stream_handler.hpp\n@@ -109,11 +109,11 @@ struct stream_handler {\n     }\n   }\n\n-  tcp_socket::endpoint_type remote_endpoint() const {\n+  tcp_socket::endpoint_type remote_endpoint(std::error_code\u0026 ec) const {\n     if (ssl_enabled) {\n-      return ssl_sock_-\u003enext_layer().remote_endpoint();\n+      return ssl_sock_-\u003enext_layer().remote_endpoint(ec);\n     } else {\n-      return tcp_sock_-\u003eremote_endpoint();\n+      return tcp_sock_-\u003eremote_endpoint(ec);\n     }\n   }\n\n```\n","author":{"url":"https://github.com/vovams","@type":"Person","name":"vovams"},"datePublished":"2016-08-08T15:07:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/677/cpp-netlib/issues/677"}