When a message is successfully received by the socket, it is
stored in the aio by an internal call equivalent to
nng_aio_set_msg(), then the completion
callback on the aio is executed.
In this case, nng_aio_result() will
return zero.
The callback function is responsible for retrieving the message
and disposing of it appropriately.
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Important
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Failing to accept and dispose of messages in this case can lead to memory leaks. |
If for some reason the asynchronous receive cannot be completed
successfully (including by being canceled or timing out), then
the callback will still be executed,
but nng_aio_result() will be non-zero.
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Note
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The semantics of what receiving a message means varies from protocol to
protocol, so examination of the protocol documentation is encouraged.
(For example, with a pub socket the data is broadcast, so that
any peers who have a suitable subscription will be able to receive it using
nng_recv() or a similar function.)
Furthermore, some protocols may not support receiving (such as
pub) or may require other conditions.
(For example, req sockets cannot normally receive data, which
are replies to requests, until they have first sent a request.)
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NNG_ECANCELED
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The operation was aborted. |
NNG_ECLOSED
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The socket s is not open. |
NNG_ENOMEM
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Insufficient memory is available. |
NNG_ENOTSUP
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The protocol for socket s does not support receiving. |
NNG_ESTATE
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The socket s cannot receive data in this state. |
NNG_ETIMEDOUT
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The receive timeout expired. |