Change default listen backlog to socket_base::max_connections

Work on #245
Related to zaphoyd/websocketpp#549

Change default listen backlog from 0 to
boost::asio::socket_base::max_connections.
Also, we'll take on the opportunity and add a configuration parameter
for this value, in the file kurento.conf.json.

kurento.conf.json

@@ -21,7 +21,10 @@
         //  "localAddress": "localhost"
         //},
         "path": "kurento",
-        "threads": 10
+        "threads": 10,
+        // Maximum queue length of pending connections (see sysctl tcp_max_syn_backlog)
+        // Default SOMAXCONN (128)
+        //"connqueue": 128,
       }
     }
   }

server/transport/websocket/WebSocketTransport.cpp

@@ -47,6 +47,8 @@ const std::string DEFAULT_LOCAL_ADDRESS = "localhost";
 const ushort WEBSOCKET_PORT_DEFAULT = 8888;
 const std::string WEBSOCKET_PATH_DEFAULT = "kurento";
 const int WEBSOCKET_THREADS_DEFAULT = 10;
+const int WEBSOCKET_CONNQUEUE_DEFAULT =
+  boost::asio::socket_base::max_connections;
 
 class configuration_exception : public std::exception
 {
@@ -71,6 +73,7 @@ WebSocketTransport::WebSocketTransport (const boost::property_tree::ptree
 {
   ushort port;
   ushort securePort;
+  int connqueue;
   std::string registrarAddress;
   std::string localAddress;
 
@@ -81,6 +84,9 @@ WebSocketTransport::WebSocketTransport (const boost::property_tree::ptree
   path = config.get<std::string> ("mediaServer.net.websocket.path",
                                   WEBSOCKET_PATH_DEFAULT);
 
+  connqueue = config.get<uint> ("mediaServer.net.websocket.connqueue",
+                                WEBSOCKET_CONNQUEUE_DEFAULT);
+
   try {
     n_threads = config.get<uint> ("mediaServer.net.websocket.threads");
 
@@ -103,6 +109,7 @@ WebSocketTransport::WebSocketTransport (const boost::property_tree::ptree
   server.clear_error_channels (websocketpp::log::alevel::all);
 
   server.init_asio (&ios);
+  server.set_listen_backlog (connqueue);
   server.set_reuse_addr (true);
   server.set_open_handler (std::bind ( (void (WebSocketTransport::*) (
                                           WebSocketServer *, websocketpp::connection_hdl) )