rpc: send clean close frame on websocket disconnect

[Sahil-4555]

Currently, when a WebSocket connection is closed by the RPC server, the underlying TCP connection gets torn down immediately without sending a final WebSocket Close frame. Because of this abrupt teardown, clients connected to the node experience an abnormal closure (error code 1006) instead of a clean, normal disconnect (error code 1000).

This PR fixes that behavior by explicitly sending a clean 1000 normal closure frame right before terminating the connection. It uses the Close() method from the coder/websocket library to safely transmit this control frame.

[Copilot]

Pull request overview

This PR aims to make RPC server–initiated WebSocket disconnects appear as a clean, normal WebSocket closure (1000) to peers, instead of an abnormal closure (1006), by explicitly sending a Close control frame before tearing down the connection.

Changes:

• Send a WebSocket Close frame (StatusNormalClosure) in websocketCodec.Close() prior to shutting down the JSON codec and ping loop.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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[yperbasis]

@Sahil-4555 fix lint plz

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

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let's address copilot's comments

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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