Merge commit '1dd2f4645226bd269f2407d5ed431acc3f66e7a6' as 'Sources/ASIO'

Sources/ASIO/asio/src/examples/cpp03/porthopper/client.cpp

@@ -0,0 +1,192 @@
+//
+// client.cpp
+// ~~~~~~~~~~
+//
+// Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff 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)
+//
+
+#include <asio.hpp>
+#include <boost/lambda/lambda.hpp>
+#include <boost/lambda/bind.hpp>
+#include <boost/lambda/if.hpp>
+#include <boost/shared_ptr.hpp>
+#include <algorithm>
+#include <cstdlib>
+#include <exception>
+#include <iostream>
+#include <string>
+#include "protocol.hpp"
+
+using namespace boost;
+using asio::ip::tcp;
+using asio::ip::udp;
+
+int main(int argc, char* argv[])
+{
+  try
+  {
+    if (argc != 3)
+    {
+      std::cerr << "Usage: client <host> <port>\n";
+      return 1;
+    }
+    using namespace std; // For atoi.
+    std::string host_name = argv[1];
+    std::string port = argv[2];
+
+    asio::io_context io_context;
+
+    // Determine the location of the server.
+    tcp::resolver resolver(io_context);
+    tcp::endpoint remote_endpoint = *resolver.resolve(host_name, port).begin();
+
+    // Establish the control connection to the server.
+    tcp::socket control_socket(io_context);
+    control_socket.connect(remote_endpoint);
+
+    // Create a datagram socket to receive data from the server.
+    boost::shared_ptr<udp::socket> data_socket(
+        new udp::socket(io_context, udp::endpoint(udp::v4(), 0)));
+
+    // Determine what port we will receive data on.
+    udp::endpoint data_endpoint = data_socket->local_endpoint();
+
+    // Ask the server to start sending us data.
+    control_request start = control_request::start(data_endpoint.port());
+    asio::write(control_socket, start.to_buffers());
+
+    unsigned long last_frame_number = 0;
+    for (;;)
+    {
+      // Receive 50 messages on the current data socket.
+      for (int i = 0; i < 50; ++i)
+      {
+        // Receive a frame from the server.
+        frame f;
+        data_socket->receive(f.to_buffers(), 0);
+        if (f.number() > last_frame_number)
+        {
+          last_frame_number = f.number();
+          std::cout << "\n" << f.payload();
+        }
+      }
+
+      // Time to switch to a new socket. To ensure seamless handover we will
+      // continue to receive packets using the old socket until data arrives on
+      // the new one.
+      std::cout << " Starting renegotiation";
+
+      // Create the new data socket.
+      boost::shared_ptr<udp::socket> new_data_socket(
+          new udp::socket(io_context, udp::endpoint(udp::v4(), 0)));
+
+      // Determine the new port we will use to receive data.
+      udp::endpoint new_data_endpoint = new_data_socket->local_endpoint();
+
+      // Ask the server to switch over to the new port.
+      control_request change = control_request::change(
+          data_endpoint.port(), new_data_endpoint.port());
+      asio::error_code control_result;
+      asio::async_write(control_socket, change.to_buffers(),
+          (
+            lambda::var(control_result) = lambda::_1
+          ));
+
+      // Try to receive a frame from the server on the new data socket. If we
+      // successfully receive a frame on this new data socket we can consider
+      // the renegotation complete. In that case we will close the old data
+      // socket, which will cause any outstanding receive operation on it to be
+      // cancelled.
+      frame f1;
+      asio::error_code new_data_socket_result;
+      new_data_socket->async_receive(f1.to_buffers(),
+          (
+            // Note: lambda::_1 is the first argument to the callback handler,
+            // which in this case is the error code for the operation.
+            lambda::var(new_data_socket_result) = lambda::_1,
+            lambda::if_(!lambda::_1)
+            [
+              // We have successfully received a frame on the new data socket,
+              // so we can close the old data socket. This will cancel any
+              // outstanding receive operation on the old data socket.
+              lambda::var(data_socket) = boost::shared_ptr<udp::socket>()
+            ]
+          ));
+
+      // This loop will continue until we have successfully completed the
+      // renegotiation (i.e. received a frame on the new data socket), or some
+      // unrecoverable error occurs.
+      bool done = false;
+      while (!done)
+      {
+        // Even though we're performing a renegotation, we want to continue
+        // receiving data as smoothly as possible. Therefore we will continue to
+        // try to receive a frame from the server on the old data socket. If we
+        // receive a frame on this socket we will interrupt the io_context,
+        // print the frame, and resume waiting for the other operations to
+        // complete.
+        frame f2;
+        done = true; // Let's be optimistic.
+        if (data_socket) // Might have been closed by new_data_socket's handler.
+        {
+          data_socket->async_receive(f2.to_buffers(), 0,
+              (
+                lambda::if_(!lambda::_1)
+                [
+                  // We have successfully received a frame on the old data
+                  // socket. Stop the io_context so that we can print it.
+                  lambda::bind(&asio::io_context::stop, &io_context),
+                  lambda::var(done) = false
+                ]
+              ));
+        }
+
+        // Run the operations in parallel. This will block until all operations
+        // have finished, or until the io_context is interrupted. (No threads!)
+        io_context.restart();
+        io_context.run();
+
+        // If the io_context.run() was interrupted then we have received a frame
+        // on the old data socket. We need to keep waiting for the renegotation
+        // operations to complete.
+        if (!done)
+        {
+          if (f2.number() > last_frame_number)
+          {
+            last_frame_number = f2.number();
+            std::cout << "\n" << f2.payload();
+          }
+        }
+      }
+
+      // Since the loop has finished, we have either successfully completed
+      // the renegotation, or an error has occurred. First we'll check for
+      // errors.
+      if (control_result)
+        throw asio::system_error(control_result);
+      if (new_data_socket_result)
+        throw asio::system_error(new_data_socket_result);
+
+      // If we get here it means we have successfully started receiving data on
+      // the new data socket. This new data socket will be used from now on
+      // (until the next time we renegotiate).
+      std::cout << " Renegotiation complete";
+      data_socket = new_data_socket;
+      data_endpoint = new_data_endpoint;
+      if (f1.number() > last_frame_number)
+      {
+        last_frame_number = f1.number();
+        std::cout << "\n" << f1.payload();
+      }
+    }
+  }
+  catch (std::exception& e)
+  {
+    std::cerr << "Exception: " << e.what() << std::endl;
+  }
+
+  return 0;
+}