tcpserver.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>
#include <event2/event.h>
#include <event2/buffer.h>
#include <event2/bufferevent.h>
#include <event2/listener.h>
#include <sys/time.h>
#include <sys/resource.h>

#define MAX_OPENFILES_DEFAULT 1024 * 1024
#define MAX_OPENFILES_TARGET  1024 * 1024 * 256

static void readcb(struct bufferevent *bev, void *ctx)
{
  /* This callback is invoked when there is data to read on bev. */
  struct evbuffer *input = bufferevent_get_input(bev);
  struct evbuffer *output = bufferevent_get_output(bev);

  /* Copy all the data from the input buffer to the output buffer. */
  evbuffer_add_buffer(output, input);
}

static void eventcb(struct bufferevent *bev, short events, void *ctx)
{
  if (events & BEV_EVENT_ERROR)
    perror("Error from bufferevent");
  if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR)) {
    bufferevent_free(bev);
  }
}

static void accept_conn_cb(struct evconnlistener *listener,
			   evutil_socket_t fd, struct sockaddr *address,
			   int socklen, void *ctx)
{
  char host[NI_MAXHOST];
  char port[NI_MAXSERV];
  getnameinfo(address, socklen, host, NI_MAXHOST, port, NI_MAXSERV,
	      NI_NUMERICHOST | NI_NUMERICSERV);
  printf("Got new connection from %s:%s\n", host, port);
  /* Setup a bufferevent */
  struct event_base *base = evconnlistener_get_base(listener);
  struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
  bufferevent_setcb(bev, readcb, NULL, eventcb, NULL);
  bufferevent_enable(bev, EV_READ|EV_WRITE);
}

static void
accept_error_cb(struct evconnlistener *listener, void *ctx)
{
  struct event_base *base = evconnlistener_get_base(listener);
  int err = EVUTIL_SOCKET_ERROR();
  fprintf(stderr, "Got an error %d (%s) on the listener. "
	  "Shutting down.\n", err, evutil_socket_error_to_string(err));

  event_base_loopexit(base, NULL);
}

int main(int argc, char** argv)
{
  struct event_base *base;
  struct evconnlistener *listener;
  struct sockaddr_in6 sin;
  struct rlimit limit_openfiles;
  FILE *nr_open;
  int ret;
  int port = 4242;

  if (argc > 1) {
    port = atoi(argv[1]);
  }
  if (port <= 0 || port > 65535) {
    fprintf(stderr, "Invalid port\n");
    return 1;
  }

  /* Setup limit on number of open files. */
  /* First, set soft limit to hard limit */
  ret = getrlimit(RLIMIT_NOFILE, &limit_openfiles);
  if (ret != 0) {
    perror("Failed to get limit on number of open files");
    return 1;
  }
  limit_openfiles.rlim_cur = limit_openfiles.rlim_max;
  ret = setrlimit(RLIMIT_NOFILE, &limit_openfiles);

  /* Then try to increase the limit to the maximum (needs to be root) */
  limit_openfiles.rlim_cur = MAX_OPENFILES_DEFAULT;
  limit_openfiles.rlim_max = MAX_OPENFILES_DEFAULT;
  ret = setrlimit(RLIMIT_NOFILE, &limit_openfiles);
  if (ret != 0) {
    perror("Failed to increase limit on number of open files to MAX_OPENFILES_DEFAULT");
    fprintf(stderr, "Try to run this program as root.\n");
  } else {
    /* Try to increase the limit even further. */
    nr_open = fopen("/proc/sys/fs/nr_open", "w");
    if (nr_open == NULL) {
      perror("Failed to open /proc/sys/fs/nr_open for writing");
    } else {
      fprintf(nr_open, "%d\n", MAX_OPENFILES_TARGET);
      fclose(nr_open);
    }
    limit_openfiles.rlim_cur = MAX_OPENFILES_TARGET;
    limit_openfiles.rlim_max = MAX_OPENFILES_TARGET;
    ret = setrlimit(RLIMIT_NOFILE, &limit_openfiles);
    if (ret != 0) {
      perror("Failed to increase limit on number of open files to MAX_OPENFILES_TARGET");
    }
  }

  /* Display final limit */
  ret = getrlimit(RLIMIT_NOFILE, &limit_openfiles);
  if (ret != 0) {
    perror("Failed to get limit on number of open files");
    return 1;
  }
  printf("Maximum number of TCP clients: %ld\n", limit_openfiles.rlim_cur);

  base = event_base_new();
  if (!base) {
    fprintf(stderr, "Couldn't open event base\n");
    return 1;
  }

  /* Clear the sockaddr before using it, in case there are extra
   * platform-specific fields that can mess us up. */
  memset(&sin, 0, sizeof(sin));
  sin.sin6_family = AF_INET6;
  /* Listen on the given port, on :: */
  sin.sin6_port = htons(port);
  listener = evconnlistener_new_bind(base, accept_conn_cb, NULL,
				     LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE, 8192,
				     (struct sockaddr*)&sin, sizeof(sin));
  if (!listener) {
    perror("Couldn't create listener");
    return 1;
  }
  char l_host[NI_MAXHOST];
  char l_port[NI_MAXSERV];
  getnameinfo((struct sockaddr*)&sin, sizeof(sin), l_host, NI_MAXHOST,
	      l_port, NI_MAXSERV, NI_NUMERICHOST | NI_NUMERICSERV);
  printf("Listening on %s port %s\n", l_host, l_port);
  evconnlistener_set_error_cb(listener, accept_error_cb);
  return event_base_dispatch(base);
}