Mongoose example for server data push

examples/server_data_push/Makefile

+# Copyright (c) 2015 Cesanta Software
+# All rights reserved
+
+PROG = server_data_push
+CFLAGS = -W -Wall -I../.. -pthread -g -O0 -DMONGOOSE_ENABLE_THREADS $(CFLAGS_EXTRA)
+SOURCES = $(PROG).c ../../mongoose.c
+
+$(PROG): $(SOURCES)
+	$(CC) -o $(PROG) $(SOURCES) $(CFLAGS)
+
+clean:
+	rm -rf $(PROG) *.exe *.dSYM *.obj *.exp .*o *.lib

examples/server_data_push/server_data_push.c

+/*
+ * Copyright (c) 2015 Cesanta Software Limited
+ *
+ * In this example we have a background data producer that periodically
+ * produces a piece of data, which is then distributed to all connected
+ * WebSocket clients.
+ *
+ * Data producing thread is outside of the event loop so synchronization
+ * using a mutex is required.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <pthread.h>
+
+#include "mongoose.h"
+
+static pthread_mutex_t s_data_lock = PTHREAD_MUTEX_INITIALIZER;
+static int s_data_version = 0;
+static char s_data[100];
+
+void *data_producer(void *arg) {
+  (void) arg;
+  fprintf(stderr, "Data producer running\n");
+  srand(time(NULL));
+  while (1) {
+    pthread_mutex_lock(&s_data_lock);
+    snprintf(s_data, sizeof(s_data), "The lucky number is %d.", rand() % 100);
+    s_data_version++;
+    pthread_mutex_unlock(&s_data_lock);
+    sleep(1 + rand() % 10);
+  }
+}
+
+struct conn_state {
+  int data_version;
+  /* More state goes here. */
+};
+
+void maybe_send_data(struct mg_connection *conn) {
+  struct conn_state *cs = (struct conn_state *) conn->connection_param;
+  if (cs == NULL) return;  /* Not connected yet. */
+  pthread_mutex_lock(&s_data_lock);
+  if (cs->data_version != s_data_version) {
+    mg_websocket_printf(conn, WEBSOCKET_OPCODE_TEXT, "%s\n", s_data);
+    cs->data_version = s_data_version;
+  }
+  pthread_mutex_unlock(&s_data_lock);
+}
+
+static int ev_handler(struct mg_connection *conn, enum mg_event ev) {
+  switch (ev) {
+    case MG_WS_CONNECT:
+      fprintf(stderr, "%s:%u joined\n", conn->remote_ip, conn->remote_port);
+      conn->connection_param = calloc(1, sizeof(struct conn_state));
+      mg_websocket_printf(conn, WEBSOCKET_OPCODE_TEXT, "Hi %p!\n", conn);
+      maybe_send_data(conn);
+      return MG_FALSE;  /* Keep the connection open. */
+    case MG_POLL:
+      maybe_send_data(conn);
+      return MG_FALSE;  /* Keep the connection open. */
+    case MG_REQUEST:
+      /* FIXME: This is a bug in Mongoose - ping requests are generated internally
+       * but responses fall through to the user who may not expect them. */
+      if (conn->is_websocket && (conn->wsbits & 0xf) == WEBSOCKET_OPCODE_PONG) {
+        return MG_TRUE;
+      }
+      return MG_FALSE;
+    case MG_CLOSE:
+      fprintf(stderr, "%s:%u went away\n", conn->remote_ip, conn->remote_port);
+      free(conn->connection_param);
+      conn->connection_param = NULL;
+      return MG_TRUE;
+    case MG_AUTH:
+      return MG_TRUE;  /* Authenticated. */
+    default:
+      return MG_FALSE;
+  }
+}
+
+int main(void) {
+  const char *listen_port = "8080";
+  struct mg_server *server;
+  const char *err;
+
+  server = mg_create_server(NULL, ev_handler);
+  err = mg_set_option(server, "listening_port", listen_port);
+  if (err != NULL) {
+    fprintf(stderr, "Error setting up listener on %s: %s\n", listen_port, err);
+  }
+
+  mg_start_thread(data_producer, NULL);
+
+  printf("Listening on %s\n", listen_port);
+  while (1) {
+    mg_poll_server(server, 100);
+  }
+
+  return 0;
+}