#include <stdint.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/select.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

#define BUF_WORDS 65536
uint32_t buf[BUF_WORDS];
char rdbuf[4096];

int main(int argc, char **argv)
{
  int sockfd, newsockfd, portno, clilen, n, ret;
  struct sockaddr_in serv_addr, cli_addr;
  int i;
  fd_set read_fds, write_fds;
  if (argc != 2) {
    fprintf(stderr, "Usage: %s <port>\n", argv[0]);
    return -1;
  }

  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  if (sockfd < 0) {
    perror("socket");
    return -2;
  }
  bzero((char *) &serv_addr, sizeof(serv_addr));
  portno = atoi(argv[1]);
  if (portno == 0 || portno > 65536) {
    fprintf(stderr, "Invalid port\n");
    return -6;
  }
  serv_addr.sin_family = AF_INET;
  serv_addr.sin_port = htons(portno);
  serv_addr.sin_addr.s_addr = INADDR_ANY;
  if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
    perror("bind");
    return -3;
  }

  if (listen(sockfd, 1) < 0) {
    perror("listen");
    return -4;
  }

  for (;;) {
    printf("listening on port %d\n", portno);
    clilen = sizeof(cli_addr);
    newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
    if (newsockfd < 0) {
        perror("accept");
        return -5;
    }
    printf("got new client\n");

    memset(buf, 0xff, sizeof(buf));
    i = 0;
    do {
      FD_ZERO(&read_fds);
      FD_ZERO(&write_fds);
      FD_SET(newsockfd, &read_fds);
      FD_SET(newsockfd, &write_fds);
      ret = select(newsockfd+1, &read_fds, &write_fds, NULL, NULL);
      if (ret == 1) {
        if (FD_ISSET(newsockfd, &read_fds)) {
          ret = recv(newsockfd, rdbuf, sizeof(rdbuf), 0);
          printf("read %d\n", ret);
        }
        if (FD_ISSET(newsockfd, &write_fds)) {
          ret = send(newsockfd, buf, sizeof(buf), 0);
//          printf("wrote %d\n", ret);
        }
      }
      buf[i++] -= 1;
      i %= BUF_WORDS;
    } while(ret > 0);
    shutdown(newsockfd, SHUT_RD|SHUT_WR);
    close(newsockfd);
  }
  close(sockfd);

  return 0;
}