Add documentation for closing WebSocket connections

[Copilot]

Users couldn't find documentation on how to close WebSocket connections. The information existed in callback type signatures but lacked discoverability and examples.

Changes

README.md - Added "Closing Connections" section with:

• Basic close via {:close, state} return tuple
• Close with custom code/reason via {:close, {close_code, message}, state}
• Programmatic close using cast messages
• WebSocket close code ranges (1000-1015 standard, 3000-3999 registered, 4000-4999 private)

lib/websockex.ex - Added module-level "Closing Connections" documentation for HexDocs visibility

Example

# Basic close
def handle_frame({:text, "shutdown"}, state) do
  {:close, state}
end

# Close with custom code
def handle_frame({:text, "error"}, state) do
  {:close, {4000, "Custom application error"}, state}
end

# Programmatic close
def close(pid), do: WebSockex.cast(pid, :close)

def handle_cast(:close, state), do: {:close, state}

All callbacks (handle_frame/2, handle_cast/2, handle_info/2, handle_ping/2, handle_pong/2) support close return tuples.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https (dns block)
• repo.hex.pm
  • Triggering command: /usr/lib/erlang/erts-13.2.2.5/bin/inet_gethost 4 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>How to shutdown/close websocket?</issue_title>
<issue_description>I couldn't find in the documentation how to close a websocket when it is no longer of any use. Is this possible? Maybe the documentation just needs a small update?</issue_description>

<agent_instructions>Please add the information on how to close the websocket connection to the documentation.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@Azolo Yeah, there's not a specific place that tells that I guess.

The answer is most of the callbacks have the option to return a {:close, state} tuple.

https://hexdocs.pm/websockex/0.4.3/WebSockex.html#c:handle_cast/2</comment_new>
<comment_new>@Azolo
This is definitely a situation where I don't know where to put that particular piece of documentation.

If you have any ideas, let me know.</comment_new>

• Fixes How to shutdown/close websocket? #93

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