CODEWITHSUNDEEP
c++boost-asio
vengy
vengy

Reputation: 2257

Any issues calling Boost C++ ASIO function close() concurrently with an async_write() on the same socket?

According to the MSDN doc for closesocket:

"A Winsock client must never issue closesocket on s concurrently with another Winsock function call."

For example, what happens if an IO completion thread detects an error and closes the socket:

client_socket_.lowest_layer().close(ec);

while concurrently another thread is about to call:

async_write(client_socket_,...)

Could both of these calls hit their underlying closesocket() and WSASend() APIs, thus causing a potential crash?

I've seen these types of crashes in ordinary C++, but wasn't sure if Boost C++ had some kind of builtin mechanism to prevent it? If not, then do these calls require a scoped locked mutex etc.,..

Thanks.

Upvotes: 1

Views: 159

Answers (1)

sehe
sehe

Reputation: 393134

If you use a strand¹ there's no real problem, though I'll submit that it's probably cleaner (much cleaner) to invoke shutdown() before/instead of close() in many scenarios.

Asio does requires you to synchronize access to the socket/stream objects (everything other than the documented thread-safe objects as io_context and strand, really). Strands fulfill the role traditionally held by critical sections.

¹ implicit or explicit, see Why do I need strand per connection when using boost::asio?

Upvotes: 1

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