async read from socket

boost_boilerplate/CMakeLists.txt

@@ -88,3 +88,8 @@ add_executable(writing_tcp_async
   src/chapter02_io/writing_tcp_async.cpp
   src/sdk.h)
 target_link_libraries(writing_tcp_async PRIVATE Threads::Threads)
+
+add_executable(reading_tcp_async
+  src/chapter02_io/reading_tcp_async.cpp
+  src/sdk.h)
+target_link_libraries(reading_tcp_async PRIVATE Threads::Threads)

boost_boilerplate/src/chapter02_io/reading_tcp_async.cpp

@@ -0,0 +1,77 @@
+#include <boost/asio.hpp>
+#include <iostream>
+#include <memory>
+
+using namespace boost;
+using namespace std;
+namespace sys = boost::system;
+namespace net = boost::asio;
+
+struct session
+{
+  std::shared_ptr<net::ip::tcp::socket> sock;
+  unique_ptr<char[]> buf;
+  size_t total_bytes_read;
+  uint32_t buf_size;
+};
+
+void Callback(const boost::system::error_code& ec,
+              size_t bytes_transferred,
+              std::shared_ptr<session> s)
+{
+  if (ec)
+  {
+    cout << "Error!"s << ec.value() << " "s << ec.what() << endl;
+
+    return;
+  }
+
+  s->total_bytes_read += bytes_transferred;
+
+  if (s->total_bytes_read == s->buf_size) return;
+
+  s->sock->async_read_some(asio::buffer(s->buf.get() + s->total_bytes_read,
+                                        s->buf_size - s->total_bytes_read),
+                           std::bind(Callback, placeholders::_1, placeholders::_2, s));
+}
+
+void ReadFromSocket(std::shared_ptr<net::ip::tcp::socket> sock)
+{
+  auto s = make_unique<session>();
+
+  const uint32_t message_size = 7;
+
+  s->buf.reset(new char [message_size]);
+  s->total_bytes_read = 0;
+  s->sock = sock;
+  s->buf_size = message_size;
+
+  s->sock->async_read_some(net::buffer(s->buf.get(), s->buf_size),
+                           std::bind(Callback, placeholders::_1, placeholders::_2, s));
+}
+
+int main()
+{
+  string raw_ip_address = "127.0.0.1"s;
+  unsigned short port_num = 3333;
+
+  try
+  {
+    net::ip::tcp::endpoint ep(net::ip::address::from_string(raw_ip_address), port_num);
+    net::io_context ios;
+
+    auto sock = make_shared<net::ip::tcp::socket>(ios, ep.protocol());
+
+    sock->connect(ep);
+
+    ReadFromSocket(sock);
+
+    ios.run();
+  }
+  catch (const sys::system_error& e)
+  {
+    cout << "Error!" << e.what() << endl;
+  }
+
+  return EXIT_SUCCESS;
+}

boost_boilerplate/src/chapter02_io/writing_tcp_async.cpp

@@ -11,7 +11,7 @@ struct session
 {
   std::shared_ptr<net::ip::tcp::socket> sock;
   string buf;
-  size_t total_bytes_written;
+  size_t total_bytes_read;
 };
 
 void callback(const sys::error_code& ec,
@@ -25,15 +25,15 @@ void callback(const sys::error_code& ec,
     return;
   }
 
-  s->total_bytes_written += bytes_transferred;
+  s->total_bytes_read += bytes_transferred;
 
-  if (s->total_bytes_written == s->buf.length())
+  if (s->total_bytes_read == s->buf.length())
   {
     return;
   }
 
-  s->sock->async_write_some(net::buffer(s->buf.c_str() + s->total_bytes_written,
-                                        s->buf.length() - s->total_bytes_written),
+  s->sock->async_write_some(net::buffer(s->buf.c_str() + s->total_bytes_read,
+                                        s->buf.length() - s->total_bytes_read),
                             std::bind(callback, placeholders::_1, placeholders::_2, s));
 }
 
@@ -42,7 +42,7 @@ void WriteToSocket(std::shared_ptr<net::ip::tcp::socket> sock)
   auto s = make_shared<session>();
 
   s->buf = string {"Hello"};
-  s->total_bytes_written = 0;
+  s->total_bytes_read = 0;
   s->sock = sock;
 
   s->sock->async_write_some(