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53 lines
2.3 KiB
Markdown
53 lines
2.3 KiB
Markdown
---
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title: Events
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---
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Mongoose accepts incoming connections, reads and writes data and calls
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specified event handlers for each connection when appropriate. A typical event
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sequence is this:
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- For an outbound connection: `MG_EV_CONNECT` -> (`MG_EV_RECV`, `MG_EV_SEND`,
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`MG_EV_POLL` ...) -> `MG_EV_CLOSE`
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- For an inbound connection: `MG_EV_ACCEPT` -> (`MG_EV_RECV`, `MG_EV_SEND`,
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`MG_EV_POLL` ...) -> `MG_EV_CLOSE`
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Below is a list of core events triggered by Mongoose (note that each protocol
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triggers protocol-specific events in addition to the core ones):
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- `MG_EV_ACCEPT`: sent when a new server connection is accepted by a listening
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connection. `void *ev_data` is `union socket_address` of the remote peer.
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- `MG_EV_CONNECT`: sent when a new outbound connection created by `mg_connect()`
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either failed or succeeded. `void *ev_data` is `int *success`. If `success`
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is 0, then the connection has been established, otherwise it contains an error code.
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See `mg_connect_opt()` function for code example.
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- `MG_EV_RECV`: New data is received and appended to the end of `recv_mbuf`.
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`void *ev_data` is `int *num_received_bytes`. Typically, event handler should
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check received data in `nc->recv_mbuf`, discard processed data by calling
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`mbuf_remove()`, set connection flags `nc->flags` if necessary (see `struct
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mg_connection`) and write data the remote peer by output functions like
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`mg_send()`.
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**WARNING**: Mongoose uses `realloc()` to expand the receive buffer. It is
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the user's responsibility to discard processed data from the beginning of the receive
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buffer, note the `mbuf_remove()` call in the example above.
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- `MG_EV_SEND`: Mongoose has written data to the remote peer and discarded
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written data from the `mg_connection::send_mbuf`. `void *ev_data` is `int
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*num_sent_bytes`.
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**NOTE**: Mongoose output functions only append data to the
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`mg_connection::send_mbuf`. They do not do any socket writes. An actual IO
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is done by `mg_mgr_poll()`. An `MG_EV_SEND` event is just a notification about
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an IO has been done.
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- `MG_EV_POLL`: Sent to all connections on each invocation of `mg_mgr_poll()`.
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This event could be used to do any housekeeping, for example check whether a
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certain timeout has expired and closes the connection or send heartbeat
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message, etc.
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- `MG_EV_TIMER`: Sent to the connection if `mg_set_timer()` was called.
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