root/opal/mca/event/libevent2022/libevent/sample/hello-world.c

DEFINITIONS

1. main
2. listener_cb
3. conn_writecb
4. conn_eventcb
5. signal_cb

   1 /*
   2   This exmple program provides a trivial server program that listens for TCP
   3   connections on port 9995.  When they arrive, it writes a short message to
   4   each client connection, and closes each connection once it is flushed.
   5 
   6   Where possible, it exits cleanly in response to a SIGINT (ctrl-c).
   7 */
   8 
   9 
  10 #include <string.h>
  11 #include <errno.h>
  12 #include <stdio.h>
  13 #include <signal.h>
  14 #ifndef WIN32
  15 #include <netinet/in.h>
  16 # ifdef _XOPEN_SOURCE_EXTENDED
  17 #  include <arpa/inet.h>
  18 # endif
  19 #include <sys/socket.h>
  20 #endif
  21 
  22 #include <event2/bufferevent.h>
  23 #include <event2/buffer.h>
  24 #include <event2/listener.h>
  25 #include <event2/util.h>
  26 #include <event2/event.h>
  27 
  28 static const char MESSAGE[] = "Hello, World!\n";
  29 
  30 static const int PORT = 9995;
  31 
  32 static void listener_cb(struct evconnlistener *, evutil_socket_t,
  33     struct sockaddr *, int socklen, void *);
  34 static void conn_writecb(struct bufferevent *, void *);
  35 static void conn_eventcb(struct bufferevent *, short, void *);
  36 static void signal_cb(evutil_socket_t, short, void *);
  37 
  38 int
  39 main(int argc, char **argv)
  40 {
  41         struct event_base *base;
  42         struct evconnlistener *listener;
  43         struct event *signal_event;
  44 
  45         struct sockaddr_in sin;
  46 #ifdef WIN32
  47         WSADATA wsa_data;
  48         WSAStartup(0x0201, &wsa_data);
  49 #endif
  50 
  51         base = event_base_new();
  52         if (!base) {
  53                 fprintf(stderr, "Could not initialize libevent!\n");
  54                 return 1;
  55         }
  56 
  57         memset(&sin, 0, sizeof(sin));
  58         sin.sin_family = AF_INET;
  59         sin.sin_port = htons(PORT);
  60 
  61         listener = evconnlistener_new_bind(base, listener_cb, (void *)base,
  62             LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, -1,
  63             (struct sockaddr*)&sin,
  64             sizeof(sin));
  65 
  66         if (!listener) {
  67                 fprintf(stderr, "Could not create a listener!\n");
  68                 return 1;
  69         }
  70 
  71         signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);
  72 
  73         if (!signal_event || event_add(signal_event, NULL)<0) {
  74                 fprintf(stderr, "Could not create/add a signal event!\n");
  75                 return 1;
  76         }
  77 
  78         event_base_dispatch(base);
  79 
  80         evconnlistener_free(listener);
  81         event_free(signal_event);
  82         event_base_free(base);
  83 
  84         printf("done\n");
  85         return 0;
  86 }
  87 
  88 static void
  89 listener_cb(struct evconnlistener *listener, evutil_socket_t fd,
  90     struct sockaddr *sa, int socklen, void *user_data)
  91 {
  92         struct event_base *base = user_data;
  93         struct bufferevent *bev;
  94 
  95         bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
  96         if (!bev) {
  97                 fprintf(stderr, "Error constructing bufferevent!");
  98                 event_base_loopbreak(base);
  99                 return;
 100         }
 101         bufferevent_setcb(bev, NULL, conn_writecb, conn_eventcb, NULL);
 102         bufferevent_enable(bev, EV_WRITE);
 103         bufferevent_disable(bev, EV_READ);
 104 
 105         bufferevent_write(bev, MESSAGE, strlen(MESSAGE));
 106 }
 107 
 108 static void
 109 conn_writecb(struct bufferevent *bev, void *user_data)
 110 {
 111         struct evbuffer *output = bufferevent_get_output(bev);
 112         if (evbuffer_get_length(output) == 0) {
 113                 printf("flushed answer\n");
 114                 bufferevent_free(bev);
 115         }
 116 }
 117 
 118 static void
 119 conn_eventcb(struct bufferevent *bev, short events, void *user_data)
 120 {
 121         if (events & BEV_EVENT_EOF) {
 122                 printf("Connection closed.\n");
 123         } else if (events & BEV_EVENT_ERROR) {
 124                 printf("Got an error on the connection: %s\n",
 125                     strerror(errno));/*XXX win32*/
 126         }
 127         /* None of the other events can happen here, since we haven't enabled
 128          * timeouts */
 129         bufferevent_free(bev);
 130 }
 131 
 132 static void
 133 signal_cb(evutil_socket_t sig, short events, void *user_data)
 134 {
 135         struct event_base *base = user_data;
 136         struct timeval delay = { 2, 0 };
 137 
 138         printf("Caught an interrupt signal; exiting cleanly in two seconds.\n");
 139 
 140         event_base_loopexit(base, &delay);
 141 }