Line data Source code
1 : //
2 : // Copyright (c) 2025 Vinnie Falco (vinnie dot falco at gmail dot com)
3 : //
4 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 : //
7 : // Official repository: https://github.com/cppalliance/corosio
8 : //
9 :
10 : #ifndef BOOST_COROSIO_TCP_SOCKET_HPP
11 : #define BOOST_COROSIO_TCP_SOCKET_HPP
12 :
13 : #include <boost/corosio/detail/config.hpp>
14 : #include <boost/corosio/detail/platform.hpp>
15 : #include <boost/corosio/detail/except.hpp>
16 : #include <boost/corosio/io_stream.hpp>
17 : #include <boost/capy/io_result.hpp>
18 : #include <boost/corosio/io_buffer_param.hpp>
19 : #include <boost/corosio/endpoint.hpp>
20 : #include <boost/capy/ex/executor_ref.hpp>
21 : #include <boost/capy/ex/execution_context.hpp>
22 : #include <boost/capy/concept/executor.hpp>
23 :
24 : #include <system_error>
25 :
26 : #include <concepts>
27 : #include <coroutine>
28 : #include <cstddef>
29 : #include <memory>
30 : #include <stop_token>
31 : #include <type_traits>
32 :
33 : namespace boost::corosio {
34 :
35 : #if BOOST_COROSIO_HAS_IOCP
36 : using native_handle_type = std::uintptr_t; // SOCKET
37 : #else
38 : using native_handle_type = int;
39 : #endif
40 :
41 : /** An asynchronous TCP socket for coroutine I/O.
42 :
43 : This class provides asynchronous TCP socket operations that return
44 : awaitable types. Each operation participates in the affine awaitable
45 : protocol, ensuring coroutines resume on the correct executor.
46 :
47 : The socket must be opened before performing I/O operations. Operations
48 : support cancellation through `std::stop_token` via the affine protocol,
49 : or explicitly through the `cancel()` member function.
50 :
51 : @par Thread Safety
52 : Distinct objects: Safe.@n
53 : Shared objects: Unsafe. A socket must not have concurrent operations
54 : of the same type (e.g., two simultaneous reads). One read and one
55 : write may be in flight simultaneously.
56 :
57 : @par Semantics
58 : Wraps the platform TCP/IP stack. Operations dispatch to
59 : OS socket APIs via the io_context reactor (epoll, IOCP,
60 : kqueue). Satisfies @ref capy::Stream.
61 :
62 : @par Example
63 : @code
64 : io_context ioc;
65 : tcp_socket s(ioc);
66 : s.open();
67 :
68 : // Using structured bindings
69 : auto [ec] = co_await s.connect(
70 : endpoint(ipv4_address::loopback(), 8080));
71 : if (ec)
72 : co_return;
73 :
74 : char buf[1024];
75 : auto [read_ec, n] = co_await s.read_some(
76 : capy::mutable_buffer(buf, sizeof(buf)));
77 : @endcode
78 : */
79 : class BOOST_COROSIO_DECL tcp_socket : public io_stream
80 : {
81 : public:
82 : /** Different ways a socket may be shutdown. */
83 : enum shutdown_type
84 : {
85 : shutdown_receive,
86 : shutdown_send,
87 : shutdown_both
88 : };
89 :
90 : /** Options for SO_LINGER socket option. */
91 : struct linger_options
92 : {
93 : bool enabled = false;
94 : int timeout = 0; // seconds
95 : };
96 :
97 : struct socket_impl : io_stream_impl
98 : {
99 : virtual std::coroutine_handle<> connect(
100 : std::coroutine_handle<>,
101 : capy::executor_ref,
102 : endpoint,
103 : std::stop_token,
104 : std::error_code*) = 0;
105 :
106 : virtual std::error_code shutdown(shutdown_type) noexcept = 0;
107 :
108 : virtual native_handle_type native_handle() const noexcept = 0;
109 :
110 : /** Request cancellation of pending asynchronous operations.
111 :
112 : All outstanding operations complete with operation_canceled error.
113 : Check `ec == cond::canceled` for portable comparison.
114 : */
115 : virtual void cancel() noexcept = 0;
116 :
117 : // Socket options
118 : virtual std::error_code set_no_delay(bool value) noexcept = 0;
119 : virtual bool no_delay(std::error_code& ec) const noexcept = 0;
120 :
121 : virtual std::error_code set_keep_alive(bool value) noexcept = 0;
122 : virtual bool keep_alive(std::error_code& ec) const noexcept = 0;
123 :
124 : virtual std::error_code set_receive_buffer_size(int size) noexcept = 0;
125 : virtual int receive_buffer_size(std::error_code& ec) const noexcept = 0;
126 :
127 : virtual std::error_code set_send_buffer_size(int size) noexcept = 0;
128 : virtual int send_buffer_size(std::error_code& ec) const noexcept = 0;
129 :
130 : virtual std::error_code set_linger(bool enabled, int timeout) noexcept = 0;
131 : virtual linger_options linger(std::error_code& ec) const noexcept = 0;
132 :
133 : /// Returns the cached local endpoint.
134 : virtual endpoint local_endpoint() const noexcept = 0;
135 :
136 : /// Returns the cached remote endpoint.
137 : virtual endpoint remote_endpoint() const noexcept = 0;
138 : };
139 :
140 : struct connect_awaitable
141 : {
142 : tcp_socket& s_;
143 : endpoint endpoint_;
144 : std::stop_token token_;
145 : mutable std::error_code ec_;
146 :
147 8853 : connect_awaitable(tcp_socket& s, endpoint ep) noexcept
148 8853 : : s_(s)
149 8853 : , endpoint_(ep)
150 : {
151 8853 : }
152 :
153 8853 : bool await_ready() const noexcept
154 : {
155 8853 : return token_.stop_requested();
156 : }
157 :
158 8853 : capy::io_result<> await_resume() const noexcept
159 : {
160 8853 : if (token_.stop_requested())
161 0 : return {make_error_code(std::errc::operation_canceled)};
162 8853 : return {ec_};
163 : }
164 :
165 : template<typename Ex>
166 : auto await_suspend(
167 : std::coroutine_handle<> h,
168 : Ex const& ex) -> std::coroutine_handle<>
169 : {
170 : return s_.get().connect(h, ex, endpoint_, token_, &ec_);
171 : }
172 :
173 : template<typename Ex>
174 8853 : auto await_suspend(
175 : std::coroutine_handle<> h,
176 : Ex const& ex,
177 : std::stop_token token) -> std::coroutine_handle<>
178 : {
179 8853 : token_ = std::move(token);
180 8853 : return s_.get().connect(h, ex, endpoint_, token_, &ec_);
181 : }
182 : };
183 :
184 : public:
185 : /** Destructor.
186 :
187 : Closes the socket if open, cancelling any pending operations.
188 : */
189 : ~tcp_socket();
190 :
191 : /** Construct a socket from an execution context.
192 :
193 : @param ctx The execution context that will own this socket.
194 : */
195 : explicit tcp_socket(capy::execution_context& ctx);
196 :
197 : /** Construct a socket from an executor.
198 :
199 : The socket is associated with the executor's context.
200 :
201 : @param ex The executor whose context will own the socket.
202 : */
203 : template<class Ex>
204 : requires (!std::same_as<std::remove_cvref_t<Ex>, tcp_socket>) &&
205 : capy::Executor<Ex>
206 : explicit tcp_socket(Ex const& ex)
207 : : tcp_socket(ex.context())
208 : {
209 : }
210 :
211 : /** Move constructor.
212 :
213 : Transfers ownership of the socket resources.
214 :
215 : @param other The socket to move from.
216 : */
217 180 : tcp_socket(tcp_socket&& other) noexcept
218 180 : : io_stream(other.context())
219 : {
220 180 : impl_ = other.impl_;
221 180 : other.impl_ = nullptr;
222 180 : }
223 :
224 : /** Move assignment operator.
225 :
226 : Closes any existing socket and transfers ownership.
227 : The source and destination must share the same execution context.
228 :
229 : @param other The socket to move from.
230 :
231 : @return Reference to this socket.
232 :
233 : @throws std::logic_error if the sockets have different execution contexts.
234 : */
235 8 : tcp_socket& operator=(tcp_socket&& other)
236 : {
237 8 : if (this != &other)
238 : {
239 8 : if (ctx_ != other.ctx_)
240 0 : detail::throw_logic_error(
241 : "cannot move socket across execution contexts");
242 8 : close();
243 8 : impl_ = other.impl_;
244 8 : other.impl_ = nullptr;
245 : }
246 8 : return *this;
247 : }
248 :
249 : tcp_socket(tcp_socket const&) = delete;
250 : tcp_socket& operator=(tcp_socket const&) = delete;
251 :
252 : /** Open the socket.
253 :
254 : Creates an IPv4 TCP socket and associates it with the platform
255 : reactor (IOCP on Windows). This must be called before initiating
256 : I/O operations.
257 :
258 : @throws std::system_error on failure.
259 : */
260 : void open();
261 :
262 : /** Close the socket.
263 :
264 : Releases socket resources. Any pending operations complete
265 : with `errc::operation_canceled`.
266 : */
267 : void close();
268 :
269 : /** Check if the socket is open.
270 :
271 : @return `true` if the socket is open and ready for operations.
272 : */
273 28 : bool is_open() const noexcept
274 : {
275 28 : return impl_ != nullptr;
276 : }
277 :
278 : /** Initiate an asynchronous connect operation.
279 :
280 : Connects the socket to the specified remote endpoint. The socket
281 : must be open before calling this function.
282 :
283 : The operation supports cancellation via `std::stop_token` through
284 : the affine awaitable protocol. If the associated stop token is
285 : triggered, the operation completes immediately with
286 : `errc::operation_canceled`.
287 :
288 : @param ep The remote endpoint to connect to.
289 :
290 : @return An awaitable that completes with `io_result<>`.
291 : Returns success (default error_code) on successful connection,
292 : or an error code on failure including:
293 : - connection_refused: No server listening at endpoint
294 : - timed_out: Connection attempt timed out
295 : - network_unreachable: No route to host
296 : - operation_canceled: Cancelled via stop_token or cancel().
297 : Check `ec == cond::canceled` for portable comparison.
298 :
299 : @throws std::logic_error if the socket is not open.
300 :
301 : @par Preconditions
302 : The socket must be open (`is_open() == true`).
303 :
304 : @par Example
305 : @code
306 : auto [ec] = co_await s.connect(endpoint);
307 : if (ec) { ... }
308 : @endcode
309 : */
310 8853 : auto connect(endpoint ep)
311 : {
312 8853 : if (!impl_)
313 0 : detail::throw_logic_error("connect: socket not open");
314 8853 : return connect_awaitable(*this, ep);
315 : }
316 :
317 : /** Cancel any pending asynchronous operations.
318 :
319 : All outstanding operations complete with `errc::operation_canceled`.
320 : Check `ec == cond::canceled` for portable comparison.
321 : */
322 : void cancel();
323 :
324 : /** Get the native socket handle.
325 :
326 : Returns the underlying platform-specific socket descriptor.
327 : On POSIX systems this is an `int` file descriptor.
328 : On Windows this is a `SOCKET` handle.
329 :
330 : @return The native socket handle, or -1/INVALID_SOCKET if not open.
331 :
332 : @par Preconditions
333 : None. May be called on closed sockets.
334 : */
335 : native_handle_type native_handle() const noexcept;
336 :
337 : /** Disable sends or receives on the socket.
338 :
339 : TCP connections are full-duplex: each direction (send and receive)
340 : operates independently. This function allows you to close one or
341 : both directions without destroying the socket.
342 :
343 : @li @ref shutdown_send sends a TCP FIN packet to the peer,
344 : signaling that you have no more data to send. You can still
345 : receive data until the peer also closes their send direction.
346 : This is the most common use case, typically called before
347 : close() to ensure graceful connection termination.
348 :
349 : @li @ref shutdown_receive disables reading on the socket. This
350 : does NOT send anything to the peer - they are not informed
351 : and may continue sending data. Subsequent reads will fail
352 : or return end-of-file. Incoming data may be discarded or
353 : buffered depending on the operating system.
354 :
355 : @li @ref shutdown_both combines both effects: sends a FIN and
356 : disables reading.
357 :
358 : When the peer shuts down their send direction (sends a FIN),
359 : subsequent read operations will complete with `capy::cond::eof`.
360 : Use the portable condition test rather than comparing error
361 : codes directly:
362 :
363 : @code
364 : auto [ec, n] = co_await sock.read_some(buffer);
365 : if (ec == capy::cond::eof)
366 : {
367 : // Peer closed their send direction
368 : }
369 : @endcode
370 :
371 : Any error from the underlying system call is silently discarded
372 : because it is unlikely to be helpful.
373 :
374 : @param what Determines what operations will no longer be allowed.
375 : */
376 : void shutdown(shutdown_type what);
377 :
378 : //--------------------------------------------------------------------------
379 : //
380 : // Socket Options
381 : //
382 : //--------------------------------------------------------------------------
383 :
384 : /** Enable or disable TCP_NODELAY (disable Nagle's algorithm).
385 :
386 : When enabled, segments are sent as soon as possible even if
387 : there is only a small amount of data. This reduces latency
388 : at the potential cost of increased network traffic.
389 :
390 : @param value `true` to disable Nagle's algorithm (enable no-delay).
391 :
392 : @throws std::logic_error if the socket is not open.
393 : @throws std::system_error on failure.
394 : */
395 : void set_no_delay(bool value);
396 :
397 : /** Get the current TCP_NODELAY setting.
398 :
399 : @return `true` if Nagle's algorithm is disabled.
400 :
401 : @throws std::logic_error if the socket is not open.
402 : @throws std::system_error on failure.
403 : */
404 : bool no_delay() const;
405 :
406 : /** Enable or disable SO_KEEPALIVE.
407 :
408 : When enabled, the socket will periodically send keepalive probes
409 : to detect if the peer is still reachable.
410 :
411 : @param value `true` to enable keepalive probes.
412 :
413 : @throws std::logic_error if the socket is not open.
414 : @throws std::system_error on failure.
415 : */
416 : void set_keep_alive(bool value);
417 :
418 : /** Get the current SO_KEEPALIVE setting.
419 :
420 : @return `true` if keepalive is enabled.
421 :
422 : @throws std::logic_error if the socket is not open.
423 : @throws std::system_error on failure.
424 : */
425 : bool keep_alive() const;
426 :
427 : /** Set the receive buffer size (SO_RCVBUF).
428 :
429 : @param size The desired receive buffer size in bytes.
430 :
431 : @throws std::logic_error if the socket is not open.
432 : @throws std::system_error on failure.
433 :
434 : @note The operating system may adjust the actual buffer size.
435 : */
436 : void set_receive_buffer_size(int size);
437 :
438 : /** Get the receive buffer size (SO_RCVBUF).
439 :
440 : @return The current receive buffer size in bytes.
441 :
442 : @throws std::logic_error if the socket is not open.
443 : @throws std::system_error on failure.
444 : */
445 : int receive_buffer_size() const;
446 :
447 : /** Set the send buffer size (SO_SNDBUF).
448 :
449 : @param size The desired send buffer size in bytes.
450 :
451 : @throws std::logic_error if the socket is not open.
452 : @throws std::system_error on failure.
453 :
454 : @note The operating system may adjust the actual buffer size.
455 : */
456 : void set_send_buffer_size(int size);
457 :
458 : /** Get the send buffer size (SO_SNDBUF).
459 :
460 : @return The current send buffer size in bytes.
461 :
462 : @throws std::logic_error if the socket is not open.
463 : @throws std::system_error on failure.
464 : */
465 : int send_buffer_size() const;
466 :
467 : /** Set the SO_LINGER option.
468 :
469 : Controls behavior when closing a socket with unsent data.
470 :
471 : @param enabled If `true`, close() will block until data is sent
472 : or the timeout expires. If `false`, close() returns immediately.
473 : @param timeout The linger timeout in seconds (only used if enabled).
474 :
475 : @throws std::logic_error if the socket is not open.
476 : @throws std::system_error on failure.
477 : */
478 : void set_linger(bool enabled, int timeout);
479 :
480 : /** Get the current SO_LINGER setting.
481 :
482 : @return The current linger options.
483 :
484 : @throws std::logic_error if the socket is not open.
485 : @throws std::system_error on failure.
486 : */
487 : linger_options linger() const;
488 :
489 : /** Get the local endpoint of the socket.
490 :
491 : Returns the local address and port to which the socket is bound.
492 : For a connected socket, this is the local side of the connection.
493 : The endpoint is cached when the connection is established.
494 :
495 : @return The local endpoint, or a default endpoint (0.0.0.0:0) if
496 : the socket is not connected.
497 :
498 : @par Thread Safety
499 : The cached endpoint value is set during connect/accept completion
500 : and cleared during close(). This function may be called concurrently
501 : with I/O operations, but must not be called concurrently with
502 : connect(), accept(), or close().
503 : */
504 : endpoint local_endpoint() const noexcept;
505 :
506 : /** Get the remote endpoint of the socket.
507 :
508 : Returns the remote address and port to which the socket is connected.
509 : The endpoint is cached when the connection is established.
510 :
511 : @return The remote endpoint, or a default endpoint (0.0.0.0:0) if
512 : the socket is not connected.
513 :
514 : @par Thread Safety
515 : The cached endpoint value is set during connect/accept completion
516 : and cleared during close(). This function may be called concurrently
517 : with I/O operations, but must not be called concurrently with
518 : connect(), accept(), or close().
519 : */
520 : endpoint remote_endpoint() const noexcept;
521 :
522 : private:
523 : friend class tcp_acceptor;
524 :
525 9183 : inline socket_impl& get() const noexcept
526 : {
527 9183 : return *static_cast<socket_impl*>(impl_);
528 : }
529 : };
530 :
531 : } // namespace boost::corosio
532 :
533 : #endif
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