sse.h File Reference

Layer 6 (Presentation) – Server-Sent Events connection pool. More...

#include "ServerConfig.h"
#include "network_drivers/transport/tcp.h"

Go to the source code of this file.

Classes
struct	SseConn
	SSE connection state stored in sse_pool[]. More...

Functions
void	sse_init ()
	Initialize all SSE pool slots to inactive.
SseConn *	sse_alloc (uint8_t slot_id, const char *path)
	Allocate an SseConn and bind it to a TCP slot.
SseConn *	sse_find (uint8_t slot_id)
	Find the SseConn for a given TCP slot, or nullptr.
void	sse_free (uint8_t slot_id)
	Free the SseConn associated with a TCP slot.
int	sse_format (char *buf, size_t n, const char *data, const char *event, const char *id)
	Format one SSE event record into a caller buffer (no transport).
bool	sse_write (SseConn *sse, const char *data, const char *event, const char *id)
	Write one SSE event record to a client.

Variables
SseConn	sse_pool [MAX_SSE_CONNS]
	Pool of SSE connection state, one per MAX_SSE_CONNS.

Detailed Description

Layer 6 (Presentation) – Server-Sent Events connection pool.

SSE (WHATWG HTML Living Standard, Server-sent events; the W3C EventSource API) is a long-lived HTTP GET response with Content-Type: text/event-stream. After the initial headers the connection stays open indefinitely; the server pushes newline-delimited event records at any time.

Event record format (WHATWG HTML, Server-sent events)

[event: <name>\n]
[id: <id>\n]
data: <payload>\n
\n

Each SseConn occupies one TCP slot from conn_pool[] for the lifetime of the subscription. The total number of simultaneous SSE connections is capped at MAX_SSE_CONNS.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file sse.h.

Function Documentation

sse_init()

void sse_init

(

)

Initialize all SSE pool slots to inactive.

Called once from DetWebServer::begin().

Definition at line 16 of file sse.cpp.

References MAX_SSE_CONNS, SseConn::sse_id, and sse_pool.

Referenced by DetWebServer::begin(), and DetWebServer::stop().

sse_alloc()

SseConn * sse_alloc	(	uint8_t	slot_id,
		const char *	path
	)

Allocate an SseConn and bind it to a TCP slot.

Parameters

slot_id	TCP slot that just received the SSE subscription request.
path	URL path the client subscribed to (stored for broadcast).

Returns

Pointer to the allocated SseConn, or nullptr if the pool is full.

Definition at line 25 of file sse.cpp.

References SseConn::active, MAX_PATH_LEN, MAX_SSE_CONNS, SseConn::path, SseConn::slot_id, SseConn::sse_id, and sse_pool.

sse_find()

SseConn * sse_find

(

uint8_t

slot_id

)

Find the SseConn for a given TCP slot, or nullptr.

Parameters

slot_id

TCP connection slot index.

Definition at line 43 of file sse.cpp.

References MAX_SSE_CONNS, and sse_pool.

Referenced by DetWebServer::http_poll_slot().

sse_free()

void sse_free

(

uint8_t

slot_id

)

Free the SseConn associated with a TCP slot.

Parameters

slot_id

TCP connection slot index.

Definition at line 53 of file sse.cpp.

References MAX_SSE_CONNS, SseConn::sse_id, and sse_pool.

sse_format()

int sse_format	(	char *	buf,
		size_t	n,
		const char *	data,
		const char *	event,
		const char *	id
	)

Format one SSE event record into a caller buffer (no transport).

Emits event: <event>\n (if event), id: <id>\n (if id), then data: <data>\n\n per the WHATWG event-stream format. data must not be nullptr. Pure: no connection state, so it is unit-testable and benchable on its own; sse_write() wraps it with the det_conn_send() I/O.

Parameters

buf	Destination buffer.
n	Size of buf.
data	Event data (required).
event	Event name (optional).
id	Event ID (optional).

Returns

Bytes written (excluding the terminator), or 0 on empty/overflow.

Definition at line 66 of file sse.cpp.

Referenced by sse_write().

sse_write()

bool sse_write	(	SseConn *	sse,
		const char *	data,
		const char *	event,
		const char *	id
	)

Write one SSE event record to a client.

Formats and sends event: ...\nid: ...\ndata: ...\n\n. Any optional field may be nullptr to omit it. data must not be nullptr.

The caller must flush the connection afterwards (det_conn_flush()) if immediate delivery is needed.

Parameters

sse	SSE connection.
data	Event data (required).
event	Event name (optional).
id	Event ID (optional).

Returns

true on success, false if the TCP slot is not active.

Definition at line 88 of file sse.cpp.

References det_conn_send(), SseConn::slot_id, SSE_BUF_SIZE, and sse_format().

Variable Documentation

sse_pool

SseConn sse_pool[MAX_SSE_CONNS]

extern

Pool of SSE connection state, one per MAX_SSE_CONNS.

Definition at line 14 of file sse.cpp.

Referenced by sse_alloc(), sse_find(), sse_free(), and sse_init().