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asio echo_server example
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Lines changed: 142 additions & 140 deletions

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‎example/asio/CMakeLists.txt‎

Lines changed: 4 additions & 128 deletions
Original file line numberDiff line numberDiff line change
@@ -7,137 +7,13 @@
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# Official repository: https://github.com/cppalliance/capy
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#
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#-------------------------------------------------
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#
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# Find or fetch Boost.Asio
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#
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#-------------------------------------------------
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if (NOT TARGET Boost::asio)
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# Use BOOST_SRC_DIR if already defined, else check env, else use default
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if (NOT DEFINED BOOST_SRC_DIR)
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if (DEFINED ENV{BOOST_SRC_DIR})
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set(BOOST_SRC_DIR "$ENV{BOOST_SRC_DIR}" CACHE STRING "Boost source dir")
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else ()
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set(BOOST_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../../.." CACHE STRING "Boost source dir")
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endif ()
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endif ()
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# Find absolute BOOST_SRC_DIR
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if (NOT IS_ABSOLUTE ${BOOST_SRC_DIR})
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set(BOOST_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/${BOOST_SRC_DIR}")
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endif ()
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# Validate BOOST_SRC_DIR
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set(BOOST_SRC_DIR_IS_VALID ON)
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foreach (F "CMakeLists.txt" "Jamroot" "boost-build.jam" "bootstrap.sh" "libs")
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if (NOT EXISTS "${BOOST_SRC_DIR}/${F}")
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set(BOOST_SRC_DIR_IS_VALID OFF)
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break()
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endif ()
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endforeach ()
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if (BOOST_SRC_DIR_IS_VALID)
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message(STATUS "Building with valid Boost src dir")
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# From BOOST_SRC_DIR
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set(BOOST_INCLUDE_LIBRARIES asio)
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set(BOOST_EXCLUDE_LIBRARIES capy)
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set(PREV_BUILD_TESTING ${BUILD_TESTING})
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set(BUILD_TESTING OFF CACHE BOOL "Build the tests." FORCE)
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add_subdirectory(${BOOST_SRC_DIR} ${CMAKE_CURRENT_BINARY_DIR}/_deps/boost EXCLUDE_FROM_ALL)
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set(BUILD_TESTING ${PREV_BUILD_TESTING} CACHE BOOL "Build the tests." FORCE)
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else ()
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# Try installed Boost package
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find_package(Boost QUIET)
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if (Boost_FOUND)
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message(STATUS "Using installed Boost package for asio example")
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if (NOT TARGET Boost::asio)
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add_library(Boost::asio ALIAS Boost::headers)
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endif ()
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else ()
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# Fallback: FetchContent
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message(STATUS "No local Boost found, using FetchContent to download Boost")
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include(FetchContent)
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# Policy CMP0135 (introduced in CMake 3.24) controls the timestamp behavior
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# for files extracted from archives downloaded via FetchContent/ExternalProject.
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#
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# OLD behavior: Extracted files keep their original timestamps from the archive.
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# This can cause build issues because archive timestamps are often
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# older than dependent build files, triggering unnecessary rebuilds
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# or causing "file has modification time in the future" warnings.
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#
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# NEW behavior: Extracted files get the current time (download time) as their
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# timestamp, which avoids these timing-related build problems.
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#
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# We set NEW if the policy exists. On older CMake versions (< 3.24), the policy
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# doesn't exist, so this block is skipped and FetchContent works normally.
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# This avoids using DOWNLOAD_EXTRACT_TIMESTAMP directly in FetchContent_Declare,
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# which would cause a parse error on CMake < 3.24 (unrecognized keyword).
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if (POLICY CMP0135)
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cmake_policy(SET CMP0135 NEW)
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endif()
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set(BOOST_INCLUDE_LIBRARIES asio)
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FetchContent_Declare(
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boost
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URL https://github.com/boostorg/boost/releases/download/boost-1.88.0/boost-1.88.0-cmake.tar.xz
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)
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set(PREV_BUILD_TESTING ${BUILD_TESTING})
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set(BUILD_TESTING OFF CACHE BOOL "Build the tests." FORCE)
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FetchContent_MakeAvailable(boost)
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set(BUILD_TESTING ${PREV_BUILD_TESTING} CACHE BOOL "Build the tests." FORCE)
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endif ()
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endif ()
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endif ()
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#-------------------------------------------------
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#
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# Example executables
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#
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#-------------------------------------------------
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file(GLOB_RECURSE PFILES CONFIGURE_DEPENDS *.cpp *.hpp
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CMakeLists.txt
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Jamfile)
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source_group(TREE ${CMAKE_CURRENT_SOURCE_DIR} PREFIX "" FILES ${PFILES})
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# any_stream example (coroutine-based)
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add_executable(capy_example_any_stream
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any_stream.cpp
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api/capy_streams.cpp
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api/capy_streams.hpp)
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set_property(TARGET capy_example_any_stream
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PROPERTY FOLDER "examples")
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target_link_libraries(capy_example_any_stream
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Boost::capy
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Boost::asio)
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# asio_callbacks example (callback-based with uni_stream)
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add_executable(capy_example_asio_callbacks
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asio_callbacks.cpp
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api/capy_streams.cpp
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api/capy_streams.hpp
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api/uni_stream.hpp)
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set_property(TARGET capy_example_asio_callbacks
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PROPERTY FOLDER "examples")
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target_link_libraries(capy_example_asio_callbacks
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Boost::capy
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Boost::asio)
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13110
# use_capy example (use_capy completion token)
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add_executable(capy_example_use_capy
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use_capy_example.cpp
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api/capy_streams.cpp
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api/capy_streams.hpp
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api/use_capy.hpp)
11+
add_executable(capy_example_asio_echo_server
12+
echo_server.cpp)
13713

138-
set_property(TARGET capy_example_use_capy
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set_property(TARGET capy_example_asio_echo_server
13915
PROPERTY FOLDER "examples")
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141-
target_link_libraries(capy_example_use_capy
17+
target_link_libraries(capy_example_asio_echo_server
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Boost::capy
14319
Boost::asio)

‎example/asio/Jamfile‎

Lines changed: 2 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -14,17 +14,7 @@ project
1414
<include>.
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;
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exe any_stream :
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any_stream.cpp
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api/capy_streams.cpp
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exe echo_server :
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echo_server.cpp
2019
;
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exe asio_callbacks :
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asio_callbacks.cpp
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api/capy_streams.cpp
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;
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exe use_capy_example :
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use_capy_example.cpp
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api/capy_streams.cpp
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;

‎example/asio/echo_server.cpp‎

Lines changed: 136 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,136 @@
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//
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// Copyright (c) 2026 Klemens Morgenstern
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/cppalliance/capy
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//
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//
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// Echo Server Example (Boost.Asio)
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//
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// A complete echo server using Boost.Asio TCP sockets with capy coroutines.
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// Demonstrates how to use capy::as_io_awaitable to await ASIO async operations.
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//
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#include <boost/capy/asio/boost.hpp>
18+
#include <boost/capy/io_task.hpp>
19+
#include <boost/capy/ex/run_async.hpp>
20+
21+
#include <boost/asio/ip/tcp.hpp>
22+
#include <boost/asio/read.hpp>
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#include <boost/asio/write.hpp>
24+
25+
#include <cstddef>
26+
#include <cstdlib>
27+
#include <iostream>
28+
29+
namespace net = boost::asio;
30+
namespace capy = boost::capy;
31+
32+
// Socket type with as_io_awaitable as the default completion token.
33+
// This allows omitting the completion token in async calls.
34+
using tcp_socket = capy::as_io_awaitable_t::as_default_on_t<
35+
net::ip::tcp::socket>;
36+
37+
using tcp_acceptor = capy::as_io_awaitable_t::as_default_on_t<
38+
net::ip::tcp::acceptor>;
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40+
// Handle a single client session.
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// Reads data from the socket and echoes it back until the connection closes.
42+
capy::io_task<> echo_session(tcp_socket sock)
43+
{
44+
char buf[1024];
45+
46+
for (;;)
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{
48+
// Read some data from the client.
49+
auto res = co_await sock.async_read_some(net::buffer(buf));
50+
51+
if (boost::system::error_code ec = res.ec; ec)
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{
53+
if (ec != net::error::eof)
54+
std::cerr << "Read error: " << ec.message() << "\n";
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break;
56+
}
57+
58+
// Write the data back to the client.
59+
res = co_await net::async_write(
60+
sock, net::buffer(buf, std::get<0>(res.values)));
61+
62+
if (res.ec)
63+
{
64+
std::cerr << "Write error: " << res.ec.message() << "\n";
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break;
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}
67+
}
68+
69+
boost::system::error_code ec;
70+
sock.shutdown(net::ip::tcp::socket::shutdown_both, ec);
71+
sock.close(ec);
72+
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co_return {};
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}
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76+
// Accept loop - accepts connections and spawns echo sessions.
77+
capy::io_task<> accept_loop(tcp_acceptor& acceptor)
78+
{
79+
auto exec = capy::wrap_asio_executor(acceptor.get_executor());
80+
auto ep = acceptor.local_endpoint();
81+
std::cout << "Listening on port " << ep.port() << "\n";
82+
83+
for (;;)
84+
{
85+
// Accept a new connection.
86+
auto [ec, sock] = co_await acceptor.async_accept();
87+
88+
if (ec)
89+
{
90+
std::cerr << "Accept error: " << ec.message() << "\n";
91+
continue;
92+
}
93+
94+
auto remote = sock.remote_endpoint();
95+
std::cout << "Connection from " << remote.address()
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<< ":" << remote.port() << "\n";
97+
98+
// Spawn an echo session for this connection.
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// Convert the socket to use as_io_awaitable as default.
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capy::run_async(exec)(
101+
echo_session(capy::as_io_awaitable_t::as_default_on(std::move(sock))));
102+
}
103+
}
104+
105+
int main(int argc, char* argv[])
106+
{
107+
unsigned short port = 8080;
108+
if (argc > 1)
109+
port = static_cast<unsigned short>(std::atoi(argv[1]));
110+
111+
try
112+
{
113+
net::io_context ioc;
114+
115+
// Create the acceptor with as_io_awaitable as default.
116+
tcp_acceptor acceptor(
117+
ioc,
118+
net::ip::tcp::endpoint(net::ip::tcp::v4(), port));
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120+
// Wrap the ASIO executor for use with capy.
121+
auto exec = capy::wrap_asio_executor(ioc.get_executor());
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123+
// Spawn the accept loop.
124+
capy::run_async(exec)(accept_loop(acceptor));
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126+
// Run the I/O context.
127+
ioc.run();
128+
}
129+
catch (std::exception const& e)
130+
{
131+
std::cerr << "Error: " << e.what() << "\n";
132+
return 1;
133+
}
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135+
return 0;
136+
}

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