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56 lines
1.8 KiB
56 lines
1.8 KiB
4 months ago
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# h2 long poll in lws
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lws server and client can support "immortal" streams that are
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not subject to normal timeouts under a special condition. These
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are read-only (to the client).
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Network connections that contain at least one immortal stream
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are themselves not subject to timeouts until the last immortal
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stream they are carrying closes.
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Because of this, it's recommended there is some other way of
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confirming that the client is still active.
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## Setting up lws server for h2 long poll
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Vhosts that wish to allow clients to serve these immortal
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streams need to set the info.options flag `LWS_SERVER_OPTION_VH_H2_HALF_CLOSED_LONG_POLL`
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at vhost creation time. The JSON config equivalent is to set
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```
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"h2-half-closed-long-poll": "1"
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```
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on the vhost. That's all that is needed.
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Streams continue to act normally for timeout with the exception
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client streams are allowed to signal they are half-closing by
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sending a zero-length DATA frame with END_STREAM set. These
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streams are allowed to exist outside of any timeout and data
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can be sent on them at will in the server -> client direction.
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## Setting client streams for long poll
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An API is provided to allow established h2 client streams to
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transition to immortal mode and send the END_STREAM to the server
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to indicate it.
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```
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int
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lws_h2_client_stream_long_poll_rxonly(struct lws *wsi);
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```
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## Example applications
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You can confirm the long poll flow simply using example applications.
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Build and run `http-server/minimal-http-server-h2-long-poll` in one
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terminal.
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In another, build the usual `http-client/minimal-http-client` example
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and run it with the flags `-l --long-poll`
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The client will connect to the server and transition to the immortal mode.
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The server sends a timestamp every minute to the client, and that will
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stay up without timeouts.
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