Prefer IP4 than IP6 when both are available

Author: philippeVerney

python/example/fetpapi.ipynb

@@ -131,6 +131,8 @@
     "    sleep(0.25)\t\n",
     "if client_session.isEtpSessionClosed():\n",
     "    print(\"The ETP session could not be established in 5 seconds.\")\n",
+    "    if not etp_server_url.endswith(\"/\"):\n",
+    "        print(\"You may try adding an ending slash to your ETP server URL.\")\n",
     "else:\n",
     "    print(\"Now connected to ETP Server\")"
    ]

src/etp/HttpClientSession.h

@@ -95,11 +95,15 @@ namespace ETP_NS
 				return;
 			}
 
+			// Reality check: IPv6 is unlikely to be available yet
+			std::vector<tcp::endpoint> endpoints(results.begin(), results.end());
+			std::stable_partition(endpoints.begin(), endpoints.end(), [](auto entry) {return entry.protocol() == tcp::v4(); });
+
 			// Make the connection on the IP address we get from a lookup
 			boost::asio::async_connect(
 				socket_,
-				results.begin(),
-				results.end(),
+				endpoints.begin(),
+				endpoints.end(),
 				std::bind(
 					&HttpClientSession::on_connect,
 					shared_from_this(),

src/etp/PlainClientSession.h

@@ -45,11 +45,15 @@ namespace ETP_NS
 				std::cerr << "on_resolve : " << ec.message() << std::endl;
 			}
 
+			// Reality check: IPv6 is unlikely to be available yet
+			std::vector<tcp::endpoint> endpoints(results.begin(), results.end());
+			std::stable_partition(endpoints.begin(), endpoints.end(), [](auto entry) {return entry.protocol() == tcp::v4(); });
+
 			// Make the connection on the IP address we get from a lookup
 			boost::asio::async_connect(
 				ws_.next_layer(),
-				results.begin(),
-				results.end(),
+				endpoints.begin(),
+				endpoints.end(),
 				std::bind(
 					&AbstractClientSessionCRTP::on_connect,
 					std::static_pointer_cast<AbstractClientSessionCRTP>(shared_from_this()),

src/etp/ssl/HttpsClientSession.h

@@ -122,11 +122,15 @@ namespace ETP_NS
 				return;
 			}
 
+			// Reality check: IPv6 is unlikely to be available yet
+			std::vector<tcp::endpoint> endpoints(results.begin(), results.end());
+			std::stable_partition(endpoints.begin(), endpoints.end(), [](auto entry) {return entry.protocol() == tcp::v4();});
+
 			// Make the connection on the IP address we get from a lookup
 			boost::asio::async_connect(
 				stream_.next_layer(),
-				results.begin(),
-				results.end(),
+				endpoints.begin(),
+				endpoints.end(),
 				std::bind(
 					&HttpsClientSession::on_connect,
 					shared_from_this(),

src/etp/ssl/SslClientSession.h

@@ -66,11 +66,15 @@ namespace ETP_NS
 				std::cerr << "on_resolve : " << ec.message() << std::endl;
 			}
 
+			// Reality check: IPv6 is unlikely to be available yet
+			std::vector<tcp::endpoint> endpoints(results.begin(), results.end());
+			std::stable_partition(endpoints.begin(), endpoints.end(), [](auto entry) {return entry.protocol() == tcp::v4(); });
+
 			// Make the connection on the IP address we get from a lookup
 			boost::asio::async_connect(
 				ws_.next_layer().next_layer(),
-				results.begin(),
-				results.end(),
+				endpoints.begin(),
+				endpoints.end(),
 				std::bind(
 					&SslClientSession::on_ssl_connect,
 					std::static_pointer_cast<SslClientSession>(shared_from_this()),