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1 | // |
2 | // client.cpp | |
3 | // ~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2016 Christopher M. Kohlhoff (chris at kohlhoff dot com) | |
6 | // | |
7 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
8 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
9 | // | |
10 | ||
11 | #include <boost/asio.hpp> | |
12 | #include <boost/lambda/lambda.hpp> | |
13 | #include <boost/lambda/bind.hpp> | |
14 | #include <boost/lambda/if.hpp> | |
15 | #include <boost/shared_ptr.hpp> | |
16 | #include <algorithm> | |
17 | #include <cstdlib> | |
18 | #include <exception> | |
19 | #include <iostream> | |
20 | #include <string> | |
21 | #include "protocol.hpp" | |
22 | ||
23 | using namespace boost; | |
24 | using boost::asio::ip::tcp; | |
25 | using boost::asio::ip::udp; | |
26 | ||
27 | int main(int argc, char* argv[]) | |
28 | { | |
29 | try | |
30 | { | |
31 | if (argc != 3) | |
32 | { | |
33 | std::cerr << "Usage: client <host> <port>\n"; | |
34 | return 1; | |
35 | } | |
36 | using namespace std; // For atoi. | |
37 | std::string host_name = argv[1]; | |
38 | std::string port = argv[2]; | |
39 | ||
40 | boost::asio::io_service io_service; | |
41 | ||
42 | // Determine the location of the server. | |
43 | tcp::resolver resolver(io_service); | |
44 | tcp::resolver::query query(host_name, port); | |
45 | tcp::endpoint remote_endpoint = *resolver.resolve(query); | |
46 | ||
47 | // Establish the control connection to the server. | |
48 | tcp::socket control_socket(io_service); | |
49 | control_socket.connect(remote_endpoint); | |
50 | ||
51 | // Create a datagram socket to receive data from the server. | |
52 | boost::shared_ptr<udp::socket> data_socket( | |
53 | new udp::socket(io_service, udp::endpoint(udp::v4(), 0))); | |
54 | ||
55 | // Determine what port we will receive data on. | |
56 | udp::endpoint data_endpoint = data_socket->local_endpoint(); | |
57 | ||
58 | // Ask the server to start sending us data. | |
59 | control_request start = control_request::start(data_endpoint.port()); | |
60 | boost::asio::write(control_socket, start.to_buffers()); | |
61 | ||
62 | unsigned long last_frame_number = 0; | |
63 | for (;;) | |
64 | { | |
65 | // Receive 50 messages on the current data socket. | |
66 | for (int i = 0; i < 50; ++i) | |
67 | { | |
68 | // Receive a frame from the server. | |
69 | frame f; | |
70 | data_socket->receive(f.to_buffers(), 0); | |
71 | if (f.number() > last_frame_number) | |
72 | { | |
73 | last_frame_number = f.number(); | |
74 | std::cout << "\n" << f.payload(); | |
75 | } | |
76 | } | |
77 | ||
78 | // Time to switch to a new socket. To ensure seamless handover we will | |
79 | // continue to receive packets using the old socket until data arrives on | |
80 | // the new one. | |
81 | std::cout << " Starting renegotiation"; | |
82 | ||
83 | // Create the new data socket. | |
84 | boost::shared_ptr<udp::socket> new_data_socket( | |
85 | new udp::socket(io_service, udp::endpoint(udp::v4(), 0))); | |
86 | ||
87 | // Determine the new port we will use to receive data. | |
88 | udp::endpoint new_data_endpoint = new_data_socket->local_endpoint(); | |
89 | ||
90 | // Ask the server to switch over to the new port. | |
91 | control_request change = control_request::change( | |
92 | data_endpoint.port(), new_data_endpoint.port()); | |
93 | boost::system::error_code control_result; | |
94 | boost::asio::async_write(control_socket, change.to_buffers(), | |
95 | ( | |
96 | lambda::var(control_result) = lambda::_1 | |
97 | )); | |
98 | ||
99 | // Try to receive a frame from the server on the new data socket. If we | |
100 | // successfully receive a frame on this new data socket we can consider | |
101 | // the renegotation complete. In that case we will close the old data | |
102 | // socket, which will cause any outstanding receive operation on it to be | |
103 | // cancelled. | |
104 | frame f1; | |
105 | boost::system::error_code new_data_socket_result; | |
106 | new_data_socket->async_receive(f1.to_buffers(), | |
107 | ( | |
108 | // Note: lambda::_1 is the first argument to the callback handler, | |
109 | // which in this case is the error code for the operation. | |
110 | lambda::var(new_data_socket_result) = lambda::_1, | |
111 | lambda::if_(!lambda::_1) | |
112 | [ | |
113 | // We have successfully received a frame on the new data socket, | |
114 | // so we can close the old data socket. This will cancel any | |
115 | // outstanding receive operation on the old data socket. | |
116 | lambda::var(data_socket) = boost::shared_ptr<udp::socket>() | |
117 | ] | |
118 | )); | |
119 | ||
120 | // This loop will continue until we have successfully completed the | |
121 | // renegotiation (i.e. received a frame on the new data socket), or some | |
122 | // unrecoverable error occurs. | |
123 | bool done = false; | |
124 | while (!done) | |
125 | { | |
126 | // Even though we're performing a renegotation, we want to continue | |
127 | // receiving data as smoothly as possible. Therefore we will continue to | |
128 | // try to receive a frame from the server on the old data socket. If we | |
129 | // receive a frame on this socket we will interrupt the io_service, | |
130 | // print the frame, and resume waiting for the other operations to | |
131 | // complete. | |
132 | frame f2; | |
133 | done = true; // Let's be optimistic. | |
134 | if (data_socket) // Might have been closed by new_data_socket's handler. | |
135 | { | |
136 | data_socket->async_receive(f2.to_buffers(), 0, | |
137 | ( | |
138 | lambda::if_(!lambda::_1) | |
139 | [ | |
140 | // We have successfully received a frame on the old data | |
141 | // socket. Stop the io_service so that we can print it. | |
142 | lambda::bind(&boost::asio::io_service::stop, &io_service), | |
143 | lambda::var(done) = false | |
144 | ] | |
145 | )); | |
146 | } | |
147 | ||
148 | // Run the operations in parallel. This will block until all operations | |
149 | // have finished, or until the io_service is interrupted. (No threads!) | |
150 | io_service.reset(); | |
151 | io_service.run(); | |
152 | ||
153 | // If the io_service.run() was interrupted then we have received a frame | |
154 | // on the old data socket. We need to keep waiting for the renegotation | |
155 | // operations to complete. | |
156 | if (!done) | |
157 | { | |
158 | if (f2.number() > last_frame_number) | |
159 | { | |
160 | last_frame_number = f2.number(); | |
161 | std::cout << "\n" << f2.payload(); | |
162 | } | |
163 | } | |
164 | } | |
165 | ||
166 | // Since the loop has finished, we have either successfully completed | |
167 | // the renegotation, or an error has occurred. First we'll check for | |
168 | // errors. | |
169 | if (control_result) | |
170 | throw boost::system::system_error(control_result); | |
171 | if (new_data_socket_result) | |
172 | throw boost::system::system_error(new_data_socket_result); | |
173 | ||
174 | // If we get here it means we have successfully started receiving data on | |
175 | // the new data socket. This new data socket will be used from now on | |
176 | // (until the next time we renegotiate). | |
177 | std::cout << " Renegotiation complete"; | |
178 | data_socket = new_data_socket; | |
179 | data_endpoint = new_data_endpoint; | |
180 | if (f1.number() > last_frame_number) | |
181 | { | |
182 | last_frame_number = f1.number(); | |
183 | std::cout << "\n" << f1.payload(); | |
184 | } | |
185 | } | |
186 | } | |
187 | catch (std::exception& e) | |
188 | { | |
189 | std::cerr << "Exception: " << e.what() << std::endl; | |
190 | } | |
191 | ||
192 | return 0; | |
193 | } |