yhirose
bef278e0d2
Samples that did not compile or run as shown: - res.user_data.get<T>() inside a generic lambda needs the `template` keyword; use explicit parameter types (tour 09, cookbook s15). - listen() on a Unix domain socket fails with port 0 (tour 09, s22). - "*.dev.local" is not a NO_PROXY pattern (c16). - ssl_backend_error() holds a verify result, not an ERR_get_error() value, after a verification failure; decode each with the matching OpenSSL function (c18). - The content provider's `length` is everything that remains, so the sample read the whole file in one call (s05). Statements corrected: - Client keep-alive is off by default; c14 is rewritten around set_keep_alive(true). - Mounted files are looked up before GET handlers (tour 04, s04). - Params keep insertion order, and to_string(Error::Connection) reads "Could not establish connection" (tour 02). - A chunked provider ends with sink.done(), and post_routing_handler runs before the response is sent (tour 09). - Timeouts surface as Error::Read; Error::Timeout comes from the stream API (c17). The max timeout cuts off the wait for the response only (c13). The progress callback needs Content-Length (c11). - Encoding selection follows q-values, then Brotli, gzip, Zstd (s08), and the client compresses with the first of those it was built with (c15). - stop() cuts a provider-driven response short (s19); a rejected content_reader already gets 400 or 413 (s07); user_data values must be copyable (s12); Client accepts a client certificate too (t04); on_message() is the fallback for every unhandled event and 204/403/404 end reconnection (e04); the pong timeout takes two to three intervals and ends a waiting read() (w02). In the LLM app tutorial, an uncaught exception does not crash the server, so say what it does instead. Drop the server and client timeout settings whose stated purpose, covering inference and download time, they do not serve: those timeouts bound a single socket wait. Update the llama.cpp server layout in chapter 7.
2.9 KiB
title, order, status
| title | order | status |
|---|---|---|
| E04. Receive SSE on the Client | 51 | draft |
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.
Basic usage
#include <httplib.h>
httplib::Client cli("http://localhost:8080");
httplib::sse::SSEClient sse(cli, "/events");
sse.on_message([](const httplib::sse::SSEMessage &msg) {
std::cout << "data: " << msg.data << std::endl;
});
sse.start(); // blocking
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.
Dispatch by event name
When the server sends events with an event: field, register a handler per name via on_event().
sse.on_event("message", [](const auto &msg) {
std::cout << "chat: " << msg.data << std::endl;
});
sse.on_event("join", [](const auto &msg) {
std::cout << msg.data << " joined" << std::endl;
});
sse.on_event("leave", [](const auto &msg) {
std::cout << msg.data << " left" << std::endl;
});
on_message() is the generic fallback: it receives every event that has no handler registered through on_event(). With on_event("message", ...) registered as above, message events go there instead.
Connection lifecycle and errors
sse.on_open([] {
std::cout << "connected" << std::endl;
});
sse.on_error([](httplib::Error err) {
std::cerr << "error: " << httplib::to_string(err) << std::endl;
});
Hook into connection open and error events. Even when the error handler fires, SSEClient keeps trying to reconnect in the background. The exceptions are a 204, 403, or 404 response, after which it stops.
Run asynchronously
If you don't want to block the main thread, use start_async().
sse.start_async();
// main thread continues to do other things
do_other_work();
// when you're done, stop it
sse.stop();
start_async() spawns a background thread to run the event loop. Use stop() to shut it down cleanly.
Configure reconnection
You can tune the reconnect interval and maximum retries.
sse.set_reconnect_interval(5000); // 5 seconds
sse.set_max_reconnect_attempts(10); // up to 10 (0 = unlimited)
If the server sends a retry: field, that takes precedence.
Automatic Last-Event-ID
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.
std::cout << "last id: " << sse.last_event_id() << std::endl;
Use last_event_id() to read the current value.
Note:
SSEClient::start()blocks, which is fine for a one-off command-line tool. For GUI apps or embedded in a server, thestart_async()+stop()pair is the usual pattern.
For the server side, see E01. Implement an SSE server.