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/client/sync-ssl/websocket_client_sync_ssl.cpp

@@ -0,0 +1,98 @@
+//
+// 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 SSL client, synchronous
+//
+//------------------------------------------------------------------------------
+
+#include "example/common/root_certificates.hpp"
+
+#include <boost/beast/core.hpp>
+#include <boost/beast/websocket.hpp>
+#include <boost/beast/websocket/ssl.hpp>
+#include <boost/asio/connect.hpp>
+#include <boost/asio/ip/tcp.hpp>
+#include <boost/asio/ssl/stream.hpp>
+#include <cstdlib>
+#include <iostream>
+#include <string>
+
+using tcp = boost::asio::ip::tcp;               // from <boost/asio/ip/tcp.hpp>
+namespace ssl = boost::asio::ssl;       // from <boost/asio/ssl.hpp>
+namespace websocket = boost::beast::websocket;  // from <boost/beast/websocket.hpp>
+
+// Sends a WebSocket message and prints the response
+int main(int argc, char** argv)
+{
+    try
+    {
+        // Check command line arguments.
+        if(argc != 4)
+        {
+            std::cerr <<
+                "Usage: websocket-client-sync-ssl <host> <port> <text>\n" <<
+                "Example:\n" <<
+                "    websocket-client-sync-ssl echo.websocket.org 443 \"Hello, world!\"\n";
+            return EXIT_FAILURE;
+        }
+        auto const host = argv[1];
+        auto const port = argv[2];
+        auto const text = argv[3];
+
+        // The io_service is required for all I/O
+        boost::asio::io_service ios;
+
+        // The SSL context is required, and holds certificates
+        ssl::context ctx{ssl::context::sslv23_client};
+
+        // This holds the root certificate used for verification
+        load_root_certificates(ctx);
+
+        // These objects perform our I/O
+        tcp::resolver resolver{ios};
+        websocket::stream<ssl::stream<tcp::socket>> ws{ios, ctx};
+
+        // Look up the domain name
+        auto const lookup = resolver.resolve({host, port});
+
+        // Make the connection on the IP address we get from a lookup
+        boost::asio::connect(ws.next_layer().next_layer(), lookup);
+
+        // Perform the SSL handshake
+        ws.next_layer().handshake(ssl::stream_base::client);
+
+        // Perform the websocket handshake
+        ws.handshake(host, "/");
+
+        // Send the message
+        ws.write(boost::asio::buffer(std::string(text)));
+
+        // This buffer will hold the incoming message
+        boost::beast::multi_buffer b;
+
+        // Read a message into our buffer
+        ws.read(b);
+
+        // Close the WebSocket connection
+        ws.close(websocket::close_code::normal);
+
+        // If we get here then the connection is closed gracefully
+
+        // The buffers() function helps print a ConstBufferSequence
+        std::cout << boost::beast::buffers(b.data()) << std::endl;
+    }
+    catch(std::exception const& e)
+    {
+        std::cerr << "Error: " << e.what() << std::endl;
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}