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/coro/CMakeLists.txt

@@ -0,0 +1,17 @@
+#
+# 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
+#
+
+GroupSources(include/boost/beast beast)
+GroupSources(example/websocket/server/coro "/")
+
+add_executable (websocket-server-coro
+    ${BOOST_BEAST_INCLUDES}
+    Jamfile
+    websocket_server_coro.cpp
+)

example/websocket/server/coro/Jamfile

@@ -0,0 +1,15 @@
+#
+# 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
+#
+
+exe websocket-server-coro :
+    websocket_server_coro.cpp
+    :
+    <variant>coverage:<build>no
+    <variant>ubasan:<build>no
+    ;

example/websocket/server/coro/websocket_server_coro.cpp

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+//
+// 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, coroutine
+//
+//------------------------------------------------------------------------------
+
+#include <boost/beast/core.hpp>
+#include <boost/beast/websocket.hpp>
+#include <boost/asio/ip/tcp.hpp>
+#include <boost/asio/spawn.hpp>
+#include <algorithm>
+#include <cstdlib>
+#include <functional>
+#include <iostream>
+#include <memory>
+#include <string>
+#include <thread>
+#include <vector>
+
+using tcp = boost::asio::ip::tcp;               // from <boost/asio/ip/tcp.hpp>
+namespace websocket = boost::beast::websocket;  // from <boost/beast/websocket.hpp>
+
+//------------------------------------------------------------------------------
+
+// Report a failure
+void
+fail(boost::system::error_code ec, char const* what)
+{
+    std::cerr << what << ": " << ec.message() << "\n";
+}
+
+// Echoes back all received WebSocket messages
+void
+do_session(tcp::socket& socket, boost::asio::yield_context yield)
+{
+    boost::system::error_code ec;
+
+    // Construct the stream by moving in the socket
+    websocket::stream<tcp::socket> ws{std::move(socket)};
+
+    // Accept the websocket handshake
+    ws.async_accept(yield[ec]);
+    if(ec)
+        return fail(ec, "accept");
+
+    for(;;)
+    {
+        // This buffer will hold the incoming message
+        boost::beast::multi_buffer buffer;
+
+        // Read a message
+        ws.async_read(buffer, yield[ec]);
+
+        // This indicates that the session was closed
+        if(ec == websocket::error::closed)
+            break;
+
+        if(ec)
+            return fail(ec, "read");
+
+        // Echo the message back
+        ws.text(ws.got_text());
+        ws.async_write(buffer.data(), yield[ec]);
+        if(ec)
+            return fail(ec, "write");
+    }
+}
+
+//------------------------------------------------------------------------------
+
+// Accepts incoming connections and launches the sessions
+void
+do_listen(
+    boost::asio::io_service& ios,
+    tcp::endpoint endpoint,
+    boost::asio::yield_context yield)
+{
+    boost::system::error_code ec;
+
+    // Open the acceptor
+    tcp::acceptor acceptor(ios);
+    acceptor.open(endpoint.protocol(), ec);
+    if(ec)
+        return fail(ec, "open");
+
+    // Bind to the server address
+    acceptor.bind(endpoint, ec);
+    if(ec)
+        return fail(ec, "bind");
+
+    // Start listening for connections
+    acceptor.listen(boost::asio::socket_base::max_connections, ec);
+    if(ec)
+        return fail(ec, "listen");
+
+    for(;;)
+    {
+        tcp::socket socket(ios);
+        acceptor.async_accept(socket, yield[ec]);
+        if(ec)
+            fail(ec, "accept");
+        else
+            boost::asio::spawn(
+                acceptor.get_io_service(),
+                std::bind(
+                    &do_session,
+                    std::move(socket),
+                    std::placeholders::_1));
+    }
+}
+
+int main(int argc, char* argv[])
+{
+    // Check command line arguments.
+    if (argc != 4)
+    {
+        std::cerr <<
+            "Usage: websocket-server-coro <address> <port> <threads>\n" <<
+            "Example:\n" <<
+            "    websocket-server-coro 0.0.0.0 8080 1\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]));
+    auto const threads = std::max<std::size_t>(1, std::atoi(argv[3]));
+
+    // The io_service is required for all I/O
+    boost::asio::io_service ios{threads};
+
+    // Spawn a listening port
+    boost::asio::spawn(ios,
+        std::bind(
+            &do_listen,
+            std::ref(ios),
+            tcp::endpoint{address, port},
+            std::placeholders::_1));
+
+    // Run the I/O service on the requested number of threads
+    std::vector<std::thread> v;
+    v.reserve(threads - 1);
+    for(auto i = threads - 1; i > 0; --i)
+        v.emplace_back(
+        [&ios]
+        {
+            ios.run();
+        });
+    ios.run();
+
+    return EXIT_SUCCESS;
+}