mirror of
https://github.com/yhirose/cpp-httplib.git
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yhirose
9bfd2ddf1c
Bring the READMEs and the docs pages (en and ja) in line with the current header: - Fix the client sample that does not compile, the Transfer-Encoding statement for default headers, the verifier callback comment, the thread pool spawn rule, the sanitize_filename description, and the inverted Accept-Encoding sentence. - Describe recent behaviour: TLS errors behind Read/Write failures, Host validation, Connection: close for a body without length, content_reader rules, refused CONNECT, WebSocketClient proxies, CPPHTTPLIB_INTERIM_RESPONSE_MAX_COUNT, the SSE event size limit, and the payload limit of the Stream API. - Complete the API references of WebSocket, WebSocketClient and the stream:: helpers, and the SSE reconnect rules. - Fix cookbook pages: keychain loading on every backend, received Close status, a multipart sample that trusted the client's file name, an echo sample that sent binary as text, SNI, pre-request handler scope, stop() with WebSocket handlers, and the thread pool notes. - Restore the mutex in the LLM app's Chapter 5 code.
92 lines
2.7 KiB
Markdown
92 lines
2.7 KiB
Markdown
---
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title: "W03. Handle Connection Close"
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order: 54
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status: "draft"
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---
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A WebSocket ends when either side closes it explicitly, or when the network drops. Handle close cleanly, and your cleanup and reconnect logic stays tidy.
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## Detect a closed connection
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When `ws.read()` returns `ReadResult::Fail`, the connection is gone — either cleanly or with an error. Break out of the loop and the handler will finish.
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```cpp
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svr.WebSocket("/chat", [](const httplib::Request &req, httplib::ws::WebSocket &ws) {
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std::string msg;
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while (ws.is_open()) {
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auto result = ws.read(msg);
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if (result == httplib::ws::ReadResult::Fail) {
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std::cout << "disconnected" << std::endl;
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break;
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}
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handle_message(ws, msg);
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}
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// cleanup runs once we're out of the loop
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cleanup_user_session(req);
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});
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```
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You can also check `ws.is_open()` — it's the same signal from a different angle.
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## Close from the server side
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To close explicitly, call `close()`.
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```cpp
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ws.close(httplib::ws::CloseStatus::Normal, "bye");
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```
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The first argument is the close status; the second is an optional reason. Common `CloseStatus` values:
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| Value | Meaning |
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| --- | --- |
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| `Normal` (1000) | Normal closure |
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| `GoingAway` (1001) | Server is shutting down |
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| `ProtocolError` (1002) | Protocol violation detected |
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| `UnsupportedData` (1003) | Received data that can't be handled |
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| `PolicyViolation` (1008) | Violated a policy |
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| `MessageTooBig` (1009) | Message too large |
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| `InternalError` (1011) | Server-side error |
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## Close from the client side
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The client API is identical.
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```cpp
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cli.close(httplib::ws::CloseStatus::Normal);
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```
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Destroying the client also closes the connection, but calling `close()` explicitly makes the intent clearer.
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## Graceful shutdown
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To notify in-flight clients that the server is going down, use `GoingAway`.
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```cpp
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ws.close(httplib::ws::CloseStatus::GoingAway, "server restarting");
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```
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On the client, `read()` just returns `Fail`; the status and reason it received aren't exposed. If the client needs to tell a restart from other closures, send it a message first (say, `ws.send("restarting")`), then call `close()`.
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## Example: a tiny chat with quit
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```cpp
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svr.WebSocket("/chat", [](const auto &req, auto &ws) {
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std::string msg;
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while (ws.is_open()) {
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if (ws.read(msg) == httplib::ws::ReadResult::Fail) break;
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if (msg == "/quit") {
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ws.send("goodbye");
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ws.close(httplib::ws::CloseStatus::Normal, "user quit");
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break;
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}
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ws.send("echo: " + msg);
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}
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});
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```
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> **Note:** On a sudden network drop, `read()` returns `Fail` with no chance to call `close()`. Put your cleanup at the end of the handler, and both paths — clean close and abrupt disconnect — end up in the same place.
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