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* Add Server::CustomRoute() for HTTP methods outside the built-in set parse_request_line validates the request method against a fixed whitelist and rejects anything else with 400 before routing runs. That blocks WebDAV, where PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, LOCK and UNLOCK are ordinary methods defined by RFC 4918, and it blocks extension methods such as UPnP's SUBSCRIBE. The need has been open since #847. Registering a handler is now what makes the server accept a method: svr.CustomRoute("PROPFIND", "/dav/:id", handler); Because custom methods go through the normal dispatch path, patterns work the way they do for Get() and friends, and the request body is available in req.body. Serving these methods through set_pre_routing_handler was never enough: the body has not been read at that point, so PROPPATCH and LOCK, which require one, could not be implemented at all. A HandlerWithContentReader overload is available too. The content reader gate in routing() also fires when a custom method carries no body, matching what expect_content() does unconditionally for POST/PUT/PATCH/DELETE, so a body-less PROPFIND (RFC 4918 treats one as allprop) reaches its handler instead of falling through to 404. Method names are validated as RFC 9110 tokens, and the ten built-in methods are refused. Seven of them are dispatched by the if/else chain in routing() before the custom tables are consulted, so a route registered for one could never fire; CONNECT, TRACE and PRI carry protocol-level meaning this library does not route. A refused registration makes is_valid() return false, so listen() fails rather than starting a server holding a handler that would never run. This is also why SSLServer::is_valid() now chains to Server::is_valid() instead of only checking ctx_. Servers that never call CustomRoute() keep the previous per-request cost: the built-in method set is checked first and short-circuits, and the custom lookup returns early on an empty map. * Add cookbook recipe for custom HTTP methods The CustomRoute() docs were a section inside S01, which pushed that page to 90 lines, the longest in the cookbook, and mixed a separate feature into a page about registering GET/POST/PUT/DELETE handlers. Move the section into its own recipe and give it room for the part that was missing: the OPTIONS handler returning DAV: and Allow, which WebDAV clients probe for before anything else. S01 goes back to 68 lines and keeps a pointer to the new page. The recipe is titled after the API rather than after WebDAV, and says outright that generating the 207 Multi-Status XML, interpreting Depth and managing locks are the reader's job. Routing the method is all the library does. S23 takes order 42, so the TLS, SSE and WebSocket recipes shift to 43-57. That only moves the sort key. Filenames, the T01/E01/W01 labels, the published URLs and every cross-reference are untouched.
100 lines
2.8 KiB
Markdown
100 lines
2.8 KiB
Markdown
---
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title: "E04. Receive SSE on the Client"
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order: 51
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status: "draft"
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---
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cpp-httplib ships a dedicated `sse::SSEClient` class. It handles auto-reconnect, per-event-name dispatch, and `Last-Event-ID` tracking for you — so receiving SSE is painless.
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## Basic usage
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```cpp
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#include <httplib.h>
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httplib::Client cli("http://localhost:8080");
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httplib::sse::SSEClient sse(cli, "/events");
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sse.on_message([](const httplib::sse::SSEMessage &msg) {
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std::cout << "data: " << msg.data << std::endl;
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});
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sse.start(); // blocking
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```
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Build an `SSEClient` with a `Client` and a path, register a callback with `on_message()`, and call `start()`. The event loop kicks in and automatically reconnects if the connection drops.
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## Dispatch by event name
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When the server sends events with an `event:` field, register a handler per name via `on_event()`.
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```cpp
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sse.on_event("message", [](const auto &msg) {
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std::cout << "chat: " << msg.data << std::endl;
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});
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sse.on_event("join", [](const auto &msg) {
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std::cout << msg.data << " joined" << std::endl;
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});
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sse.on_event("leave", [](const auto &msg) {
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std::cout << msg.data << " left" << std::endl;
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});
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```
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`on_message()` serves as a generic fallback for unnamed events (the default `message` type).
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## Connection lifecycle and errors
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```cpp
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sse.on_open([] {
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std::cout << "connected" << std::endl;
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});
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sse.on_error([](httplib::Error err) {
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std::cerr << "error: " << httplib::to_string(err) << std::endl;
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});
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```
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Hook into connection open and error events. Even when the error handler fires, `SSEClient` keeps trying to reconnect in the background.
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## Run asynchronously
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If you don't want to block the main thread, use `start_async()`.
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```cpp
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sse.start_async();
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// main thread continues to do other things
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do_other_work();
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// when you're done, stop it
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sse.stop();
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```
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`start_async()` spawns a background thread to run the event loop. Use `stop()` to shut it down cleanly.
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## Configure reconnection
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You can tune the reconnect interval and maximum retries.
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```cpp
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sse.set_reconnect_interval(5000); // 5 seconds
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sse.set_max_reconnect_attempts(10); // up to 10 (0 = unlimited)
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```
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If the server sends a `retry:` field, that takes precedence.
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## Automatic Last-Event-ID
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`SSEClient` tracks the `id` of each received event internally and sends it back as `Last-Event-ID` on reconnect. As long as the server sends events with `id:`, this all works automatically.
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```cpp
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std::cout << "last id: " << sse.last_event_id() << std::endl;
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```
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Use `last_event_id()` to read the current value.
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> **Note:** `SSEClient::start()` blocks, which is fine for a one-off command-line tool. For GUI apps or embedded in a server, the `start_async()` + `stop()` pair is the usual pattern.
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> For the server side, see [E01. Implement an SSE server](../e01-sse-server).
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