boost socket set_option timeout

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How to set a timeout on blocking sockets in boost asio?

FULL ANSWER This question keep being asked over and over again for many years. Answers I saw so far are quite poor. I’ll add this info right here in one of the first occurrences of this question.

Everybody trying to use ASIO to simplify their networking code would be perfectly happy if the author would just add an optional parameter timeout to all sync and async io functions. Unfortunately, this is unlikely to happen (in my humble opinion, just for ideological reasons, after all, AS in ASIO is for a reason).

So these are the ways to skin this poor cat available so far, none of them especially appetizing. Let’s say we need 200ms timeout.

1) Good (bad) old socket API:

Please note those peculiarities: – const int for timeout – on Windows the required type is actually DWORD, but the current set of compilers luckily has it the same, so const int will work both in Win and Posix world. – (const char*) for value. On Windows const char* is required, Posix requires const void*, in C++ const char* will convert to const void* silently while the opposite is not true.

Advantages: works and probably will always work as the socket API is old and stable. Simple enough. Fast. Disadvantages: technically might require appropriate header files (different on Win and even different UNIX flavors) for setsockopt and the macros, but current implementation of ASIO pollutes global namespace with them anyway. Requires a variable for timeout. Not type-safe. On Windows, requires that the socket is in overlapped mode to work (which current ASIO implementation luckily uses, but it is still an implementation detail). UGLY!

2) Custom ASIO socket option:

Advantages: Simple enough. Fast. Beautiful (with typedef). Disadvantages: Depends on ASIO implementation detail, which might change (but OTOH everything will change eventually, and such detail is less likely to change then public APIs subject to standardization). But in case this happens, you’ll have to either write a class according to https://www.boost.org/doc/libs/1_68_0/doc/html/boost_asio/reference/SettableSocketOption.html (which is of course a major PITA thanks to obvious overengineering of this part of ASIO) or better yet revert to 1.

3) Use C++ async/future facilities.

Advantages: standard. Disadvantages: always starts a new thread (in practice), which is relatively slow (might be good enough for clients, but will lead to DoS vulnerability for servers as threads and sockets are “expensive” resources). Don’t try to use std::launch::deferred instead of std::launch::async to avoid new thread launch as wait_for will always return future_status::deferred without trying to run the code.

4) The method prescribed by ASIO – use async operations only (which is not really the answer to the question).

Advantages: good enough for servers too if huge scalability for short transactions is not required. Disadvantages: quite wordy (so I will not even include examples – see ASIO examples). Requires very careful lifetime management of all your objects used both by async operations and their completion handlers, which in practice requires all classes containing and using such data in async operations be derived from enable_shared_from_this, which requires all such classes allocated on heap, which means (at least for short operations) that scalability will start taper down after about 16 threads as every heap alloc/dealloc will use a memory barrier.

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Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu , C++ Coding Standards

set_timeout_service_options

Set timeout service options in an execution context.

Defined in header < boost/beast/experimental/core/timeout_service.hpp >

Description

This changes the time interval for all timeouts associated with the execution context. The option must be set before any timeout objects are constructed.

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Websocket - setting a timeout for recv() (not async) #2369

flashnuke commented Jan 3, 2022

madmongo1 commented Jan 3, 2022

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vinniefalco commented Jan 3, 2022

Flashnuke commented jan 5, 2022.

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• Function Reference
• Other Services
• Socket Functions

socket_set_option

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

socket_set_option — Sets socket options for the socket

Description

The socket_set_option() function sets the option specified by the option parameter, at the specified protocol level , to the value pointed to by the value parameter for the socket .

A Socket instance created with socket_create() or socket_accept() .

The level parameter specifies the protocol level at which the option resides. For example, to set options at the socket level, a level parameter of SOL_SOCKET would be used. Other levels, such as TCP, can be used by specifying the protocol number of that level. Protocol numbers can be found by using the getprotobyname() function.

The available socket options are the same as those for the socket_get_option() function.

The option value.

Return Values

Returns true on success or false on failure.

Example #1 socket_set_option() example

• socket_create() - Create a socket (endpoint for communication)
• socket_bind() - Binds a name to a socket
• socket_strerror() - Return a string describing a socket error
• socket_last_error() - Returns the last error on the socket
• socket_get_option() - Gets socket options for the socket

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User contributed notes 8 notes.

Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu , C++ Coding Standards

While basic_stream and tcp_stream support timeouts on general logical operations, the websocket stream has a more sophisticated timeout mechanism built-in which may be enabled and configured. The timeout features of the TCP or basic stream should not be used when working with a websocket stream. The interface to these timeout features is shown in this table.

Table 1.36. WebSocket Timeout Interface

There are three timeout settings which may be set independently on the stream:

Table 1.37. WebSocket Timeout Interface (2)

By default, timeouts on websocket streams are disabled. The easiest way to turn them on is to set the suggested timeout settings on the stream.

For manual control over the settings, a timeout options object may be constructed. Here we enable only the handshake timeout.

Timeout notifications are delivered to the caller by invoking the completion handler for an outstanding asynchronous read operation with the error code error :: timeout . The implementation will close the socket or stream before delivering this error. It is not necessary to manually shut down the connection, as it will already be shut down. A read operation must be outstanding for the error to be delivered.

The timeouts on the websocket stream are incompatible with the timeouts used in the tcp_stream . When constructing a websocket stream from a tcp stream that has timeouts enabled, the timeout should be disabled first before constructing the websocket stream, as shown.

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 )