HTTP server example

To create an HTTP server, follow this pattern:

  1. Create a listening connection by calling mg_bind() or mg_bind_opt()
  2. Call mg_set_protocol_http_websocket() for that listening connection. That attaches a built-in HTTP event handler which parses incoming data and triggers HTTP-specific events. For example, when an HTTP request is fully buffered, a built-in HTTP handler parses the request and calls user-defined event handler with MG_EV_HTTP_REQUEST event and parsed HTTP request as an event data.
  3. Create event handler function. Note that event handler receives all events - low level TCP events like MG_EV_RECV and high-level HTTP events like MG_EV_HTTP_REQUEST. Normally, an event handler function should only handle MG_EV_HTTP_REQUEST event.

Here's an example of the simplest HTTP server. Error checking is omitted for the sake of clarity:

#include "mongoose.h"

static const char *s_http_port = "8000";

static void ev_handler(struct mg_connection *c, int ev, void *p) {
  if (ev == MG_EV_HTTP_REQUEST) {
    struct http_message *hm = (struct http_message *) p;

    // We have received an HTTP request. Parsed request is contained in `hm`.
    // Send HTTP reply to the client which shows full original request.
    mg_send_head(c, 200, hm->message.len, "Content-Type: text/plain");
    mg_printf(c, "%.*s", (int)hm->message.len, hm->message.p);

int main(void) {
  struct mg_mgr mgr;
  struct mg_connection *c;

  mg_mgr_init(&mgr, NULL);
  c = mg_bind(&mgr, s_http_port, ev_handler);

  for (;;) {
    mg_mgr_poll(&mgr, 1000);

  return 0;

See full HTTP server example.