https://github.com/yhirose/cpp-httplib
A C++ header-only HTTP/HTTPS server and client library
https://github.com/yhirose/cpp-httplib
cpp cpp11 header-only http https
Last synced: about 2 hours ago
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A C++ header-only HTTP/HTTPS server and client library
- Host: GitHub
- URL: https://github.com/yhirose/cpp-httplib
- Owner: yhirose
- License: mit
- Created: 2012-09-22T02:38:32.000Z (over 13 years ago)
- Default Branch: master
- Last Pushed: 2026-02-21T13:56:12.000Z (7 days ago)
- Last Synced: 2026-02-21T20:31:57.718Z (7 days ago)
- Topics: cpp, cpp11, header-only, http, https
- Language: C++
- Homepage:
- Size: 5.24 MB
- Stars: 16,157
- Watchers: 192
- Forks: 2,640
- Open Issues: 2
-
Metadata Files:
- Readme: README-sse.md
- License: LICENSE
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README
# SSEClient - Server-Sent Events Client
A simple, EventSource-like SSE client for C++11.
## Features
- **Auto-reconnect**: Automatically reconnects on connection loss
- **Last-Event-ID**: Sends last received ID on reconnect for resumption
- **retry field**: Respects server's reconnect interval
- **Event types**: Supports custom event types via `on_event()`
- **Async support**: Run in background thread with `start_async()`
- **C++11 compatible**: No C++14/17/20 features required
## Quick Start
```cpp
httplib::Client cli("http://localhost:8080");
httplib::sse::SSEClient sse(cli, "/events");
sse.on_message([](const httplib::sse::SSEMessage &msg) {
std::cout << "Event: " << msg.event << std::endl;
std::cout << "Data: " << msg.data << std::endl;
});
sse.start(); // Blocking, with auto-reconnect
```
## API Reference
### SSEMessage
```cpp
struct SSEMessage {
std::string event; // Event type (default: "message")
std::string data; // Event payload
std::string id; // Event ID
};
```
### SSEClient
#### Constructor
```cpp
// Basic
SSEClient(Client &client, const std::string &path);
// With custom headers
SSEClient(Client &client, const std::string &path, const Headers &headers);
```
#### Event Handlers
```cpp
// Called for all events (or events without a specific handler)
sse.on_message([](const SSEMessage &msg) { });
// Called for specific event types
sse.on_event("update", [](const SSEMessage &msg) { });
sse.on_event("delete", [](const SSEMessage &msg) { });
// Called when connection is established
sse.on_open([]() { });
// Called on connection errors
sse.on_error([](httplib::Error err) { });
```
#### Configuration
```cpp
// Set reconnect interval (default: 3000ms)
sse.set_reconnect_interval(5000);
// Set max reconnect attempts (default: 0 = unlimited)
sse.set_max_reconnect_attempts(10);
```
#### Control
```cpp
// Blocking start with auto-reconnect
sse.start();
// Non-blocking start (runs in background thread)
sse.start_async();
// Stop the client (thread-safe)
sse.stop();
```
#### State
```cpp
bool connected = sse.is_connected();
const std::string &id = sse.last_event_id();
```
## Examples
### Basic Usage
```cpp
httplib::Client cli("http://localhost:8080");
httplib::sse::SSEClient sse(cli, "/events");
sse.on_message([](const httplib::sse::SSEMessage &msg) {
std::cout << msg.data << std::endl;
});
sse.start();
```
### With Custom Event Types
```cpp
httplib::sse::SSEClient sse(cli, "/events");
sse.on_event("notification", [](const httplib::sse::SSEMessage &msg) {
std::cout << "Notification: " << msg.data << std::endl;
});
sse.on_event("update", [](const httplib::sse::SSEMessage &msg) {
std::cout << "Update: " << msg.data << std::endl;
});
sse.start();
```
### Async with Stop
```cpp
httplib::sse::SSEClient sse(cli, "/events");
sse.on_message([](const httplib::sse::SSEMessage &msg) {
std::cout << msg.data << std::endl;
});
sse.start_async(); // Returns immediately
// ... do other work ...
sse.stop(); // Stop when done
```
### With Custom Headers (e.g., Authentication)
```cpp
httplib::Headers headers = {
{"Authorization", "Bearer token123"}
};
httplib::sse::SSEClient sse(cli, "/events", headers);
sse.start();
```
### Error Handling
```cpp
sse.on_error([](httplib::Error err) {
std::cerr << "Error: " << httplib::to_string(err) << std::endl;
});
sse.set_reconnect_interval(1000);
sse.set_max_reconnect_attempts(5);
sse.start();
```
## SSE Protocol
The client parses SSE format according to the [W3C specification](https://html.spec.whatwg.org/multipage/server-sent-events.html):
```
event: custom-type
id: 123
data: {"message": "hello"}
data: simple message
: this is a comment (ignored)
```