Refactor all examples:

fix #575, fix #604, fix #608, fix #634, fix #712

All examples are rewritten:

* Using Best Practices
* Mostly self-contained
* New examples to complete the feature matrix
* The server-framework example is removed

example/websocket/server/sync/websocket_server_sync.cpp

@@ -0,0 +1,109 @@
+//
+// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+//------------------------------------------------------------------------------
+//
+// Example: WebSocket server, synchronous
+//
+//------------------------------------------------------------------------------
+
+#include <boost/beast/core.hpp>
+#include <boost/beast/websocket.hpp>
+#include <boost/asio/ip/tcp.hpp>
+#include <cstdlib>
+#include <functional>
+#include <iostream>
+#include <string>
+#include <thread>
+
+using tcp = boost::asio::ip::tcp;               // from <boost/asio/ip/tcp.hpp>
+namespace websocket = boost::beast::websocket;  // from <boost/beast/websocket.hpp>
+
+//------------------------------------------------------------------------------
+
+// Echoes back all received WebSocket messages
+void
+do_session(tcp::socket& socket)
+{
+    try
+    {
+        // Construct the stream by moving in the socket
+        websocket::stream<tcp::socket> ws{std::move(socket)};
+
+        // Accept the websocket handshake
+        ws.accept();
+
+        for(;;)
+        {
+            // This buffer will hold the incoming message
+            boost::beast::multi_buffer buffer;
+
+            // Read a message
+            ws.read(buffer);
+
+            // Echo the message back
+            ws.text(ws.got_text());
+            ws.write(buffer.data());
+        }
+    }
+    catch(boost::system::system_error const& se)
+    {
+        // This indicates that the session was closed
+        if(se.code() != websocket::error::closed)
+            std::cerr << "Error: " << se.code().message() << std::endl;
+    }
+    catch(std::exception const& e)
+    {
+        std::cerr << "Error: " << e.what() << std::endl;
+    }
+}
+
+//------------------------------------------------------------------------------
+
+int main(int argc, char* argv[])
+{
+    try
+    {
+        // Check command line arguments.
+        if (argc != 3)
+        {
+            std::cerr <<
+                "Usage: websocket-server-sync <address> <port>\n" <<
+                "Example:\n" <<
+                "    websocket-server-sync 0.0.0.0 8080\n";
+            return EXIT_FAILURE;
+        }
+        auto const address = boost::asio::ip::address::from_string(argv[1]);
+        auto const port = static_cast<unsigned short>(std::atoi(argv[2]));
+
+        // The io_service is required for all I/O
+        boost::asio::io_service ios{1};
+
+        // The acceptor receives incoming connections
+        tcp::acceptor acceptor{ios, {address, port}};
+        for(;;)
+        {
+            // This will receive the new connection
+            tcp::socket socket{ios};
+
+            // Block until we get a connection
+            acceptor.accept(socket);
+
+            // Launch the session, transferring ownership of the socket
+            std::thread{std::bind(
+                &do_session,
+                std::move(socket))}.detach();
+        }
+    }
+    catch (const std::exception& e)
+    {
+        std::cerr << "Error: " << e.what() << std::endl;
+        return EXIT_FAILURE;
+    }
+}