[/
 / Copyright (c) 2003-2021 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)
 /]

[section:iostreams Socket Iostreams]

Asio includes classes that implement iostreams on top of sockets. These hide
away the complexities associated with endpoint resolution, protocol
independence, etc. To create a connection one might simply write:

  ip::tcp::iostream stream("www.boost.org", "http");
  if (!stream)
  {
    // Can't connect.
  }

The iostream class can also be used in conjunction with an acceptor to create
simple servers. For example:

  io_context ioc;

  ip::tcp::endpoint endpoint(tcp::v4(), 80);
  ip::tcp::acceptor acceptor(ios, endpoint);

  for (;;)
  {
    ip::tcp::iostream stream;
    acceptor.accept(stream.socket());
    ...
  }

Timeouts may be set by calling `expires_at()` or `expires_from_now()` to
establish a deadline. Any socket operations that occur past the deadline will
put the iostream into a "bad" state.

For example, a simple client program like this:

  ip::tcp::iostream stream;
  stream.expires_from_now(boost::posix_time::seconds(60));
  stream.connect("www.boost.org", "http");
  stream << "GET /LICENSE_1_0.txt HTTP/1.0\r\n";
  stream << "Host: www.boost.org\r\n";
  stream << "Accept: */*\r\n";
  stream << "Connection: close\r\n\r\n";
  stream.flush();
  std::cout << stream.rdbuf();

will fail if all the socket operations combined take longer than 60 seconds.

If an error does occur, the iostream's `error()` member function may be used to
retrieve the error code from the most recent system call:

  if (!stream)
  {
    std::cout << "Error: " << stream.error().message() << "\n";
  }

[heading See Also]

[link asio.reference.ip__tcp.iostream ip::tcp::iostream],
[link asio.reference.basic_socket_iostream basic_socket_iostream],
[link asio.examples.cpp03_examples.iostreams iostreams examples].

[heading Notes]

These iostream templates only support `char`, not `wchar_t`, and do not perform
any code conversion.

[endsect]
