boost socket set_option timeout

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/beast: idle timeout of websocket can be delivered to caller by async_write? #1712

asdfping commented Sep 25, 2019 • edited

vinniefalco commented Sep 25, 2019

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setsockopt function (winsock.h)

The setsockopt function sets a socket option.

A descriptor that identifies a socket.

The level at which the option is defined (for example, SOL_SOCKET).

[in] optname

The socket option for which the value is to be set (for example, SO_BROADCAST). The optname parameter must be a socket option defined within the specified level , or behavior is undefined.

[in] optval

A pointer to the buffer in which the value for the requested option is specified.

[in] optlen

The size, in bytes, of the buffer pointed to by the optval parameter.

Return value

If no error occurs, setsockopt returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError .

The setsockopt function sets the current value for a socket option associated with a socket of any type, in any state. Although options can exist at multiple protocol levels, they are always present at the uppermost socket level. Options affect socket operations, such as whether expedited data (OOB data for example) is received in the normal data stream, and whether broadcast messages can be sent on the socket.

The following tables list some of the common options supported by the setsockopt function. The Type column identifies the type of data addressed by optval parameter. The Description column provides some basic information about the socket option. For more complete lists of socket options and more detailed information (default values, for example), see the detailed topics under Socket Options .

level = SOL_SOCKET

level = IPPROTO_TCP

See TCP_NODELAY in IPPROTO_TCP socket options . Also see that topic for more complete and detailed information about socket options for level = IPPROTO_TCP .

level = NSPROTO_IPX

For more complete and detailed information about socket options for level = NSPROTO_IPX , see NSPROTO_IPX Socket Options .

BSD options not supported for setsockopt are shown in the following table.

Example Code

Notes for irda sockets.

When developing applications using Windows sockets for IrDA, note the following:

• The Af_irda.h header file must be explicitly included.

The IRLMP_IAS_SET socket option enables the application to set a single attribute of a single class in the local IAS. The application specifies the class to set, the attribute, and attribute type. The application is expected to allocate a buffer of the necessary size for the passed parameters.

IrDA provides an IAS database that stores IrDA-based information. Limited access to the IAS database is available through the Windows Sockets 2 interface, but such access is not normally used by applications, and exists primarily to support connections to non-Windows devices that are not compliant with the Windows Sockets 2 IrDA conventions.

The following structure, IAS_SET , is used with the IRLMP_IAS_SET setsockopt option to manage the local IAS database:

The following structure, IAS_QUERY , is used with the IRLMP_IAS_QUERY setsockopt option to query a peer's IAS database:

Many SO_ level socket options are not meaningful to IrDA. Only SO_LINGER is specifically supported.

Windows Phone 8: This function is supported for Windows Phone Store apps on Windows Phone 8 and later.

Windows 8.1 and Windows Server 2012 R2 : This function is supported for Windows Store apps on Windows 8.1, Windows Server 2012 R2, and later.

Requirements

IPPROTO_IP Socket Options

IPPROTO_IPV6 Socket Options

IPPROTO_RM Socket Options

IPPROTO_TCP Socket Options

IPPROTO_UDP Socket Options

NSPROTO_IPX Socket Options

SOL_APPLETALK Socket Options

SOL_IRLMP Socket Options

SOL_SOCKET Socket Options

Socket Options

WSAAsyncSelect

WSAEventSelect

Winsock Functions

ioctlsocket

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Additional resources

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 )

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

socket_base::linger

Socket option to specify whether the socket lingers on close if unsent data is present.

Implements the SOL_SOCKET/SO_LINGER socket option.

Setting the option:

Getting the current option value:

Requirements

Header: boost/asio/socket_base.hpp

Convenience header: boost/asio.hpp

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 )

Make Me Engineer

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.

Related Contents:

• Why do I need strand per connection when using boost::asio?
• What is the usefulness of `enable_shared_from_this`?
• How to create a thread pool using boost in C++?
• Should the exception thrown by boost::asio::io_service::run() be caught?
• Best documentation for Boost:asio?
• Cancelling boost asio deadline timer safely
• boost asio ssl async_shutdown always finishes with an error?
• Boost async_* functions and shared_ptr’s
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