mongoose/examples/udp_echo_server/echo_server.c

// Copyright (c) 2016 Cesanta Software Limited
// All rights reserved
//
// This software is dual-licensed: you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation. For the terms of this
// license, see <http://www.gnu.org/licenses/>.
//
// You are free to use this software under the terms of the GNU General
// Public License, but WITHOUT ANY WARRANTY; without even the implied
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// Alternatively, you can license this software under a commercial
// license, as set out in <https://www.cesanta.com/license>.
//

#include "mongoose.h"

static void ev_handler(struct mg_connection *nc, int ev, void *p) {
  struct mbuf *io = &nc->recv_mbuf;
  (void) p;
  switch (ev) {
    case MG_EV_RECV:
      mg_send(nc, io->buf, io->len);  // Echo message back
      mbuf_remove(io, io->len);       // Discard message from recv buffer
      // In case of UDP, Mongoose creates new virtual connection for
      // incoming messages
      // We can keep it (and it will be reused for another messages from
      // the same address) or we can close it (this saves some memory, but
      // decreases perfomance, because it forces creation of connection
      // for every incoming dgram)
      nc->flags |= MG_F_SEND_AND_CLOSE;
      break;
    default:
      break;
  }
}

int main(void) {
  struct mg_mgr mgr;
  const char *port1 = "udp://1234", *port2 = "udp://127.0.0.1:17000";

  mg_mgr_init(&mgr, NULL);
  mg_bind(&mgr, port1, ev_handler);
  mg_bind(&mgr, port2, ev_handler);

  printf("Starting echo mgr on ports %s, %s\n", port1, port2);
  for (;;) {
    mg_mgr_poll(&mgr, 1000);
  }
  mg_mgr_free(&mgr);

  return 0;
}