geoipc/main.c

#include <stdio.h>
#include <arpa/inet.h>
#include <assert.h>
#include <netdb.h> /* getprotobyname */
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <unistd.h>

#define HOST_DNS_NAME "ifconfig.me"

#define LENGHT_OF_SUBTRACT_STRING 14

#define _XOPEN_SOURCE 255
#define TIMEOUT_SECONDS 0.01
#define DEBUG_MODE false
#define ERROR_MODE false
#define TIME_IN_SLEEP 0.01
#define TIME_LIVE_LOOP_SLEEP 0.01


void printStringWithOffset(const char* str, int start, int end) {
    int i = 0;

    for (i = start; i < end; i++) {
        write(STDERR_FILENO, &str[i], 1);
    }

    write(STDERR_FILENO, "\n", 2);
}

int
request(char *hostname_arg) {
  char buffer[BUFSIZ];
  enum CONSTEXPR { MAX_REQUEST_LEN = 1024 };
  char request[MAX_REQUEST_LEN];
  char request_template[] = "GET / HTTP/1.1\r\nHost: %s\r\n\r\n";
  struct protoent *protoent;
  char *hostname = hostname_arg; // HOST_DNS_NAME
  in_addr_t in_addr;
  int request_len;
  int socket_file_descriptor;
  ssize_t nbytes_total, nbytes_last;
  struct hostent *hostent;
  struct sockaddr_in sockaddr_in;
  unsigned short server_port = 80;

#if 0
  if (argc > 1)
    hostname = argv[1];
  if (argc > 2)
    server_port = strtoul(argv[2], NULL, 10);
#endif

  request_len = snprintf(request, MAX_REQUEST_LEN, request_template, hostname);
  if (request_len >= MAX_REQUEST_LEN) {
    #if ERROR_MODE
    fprintf(stderr, "request length large: %d\n", request_len);
    #endif
    exit(EXIT_FAILURE);
  }

  // Set timeout for the socket
  struct timeval timeout;
  timeout.tv_sec = TIMEOUT_SECONDS;
  timeout.tv_usec = 0;
  setsockopt(socket_file_descriptor, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout,
             sizeof(timeout));

  /* Build the socket. */
  protoent = getprotobyname("tcp");
  if (protoent == NULL) {
    perror("getprotobyname");
    return -3;
    // exit(EXIT_FAILURE);
  }
  socket_file_descriptor = socket(AF_INET, SOCK_STREAM, protoent->p_proto);
  if (socket_file_descriptor == -1) {
    perror("socket");
    return -3;
    // exit(EXIT_FAILURE);
  }

  /* Build the address. */
  hostent = gethostbyname(hostname);
  if (hostent == NULL) {
    #if ERROR_MODE
    fprintf(stderr, "error: gethostbyname(\"%s\")\n", hostname);
    #endif
    return -3;
    // exit(EXIT_FAILURE);
  }
  in_addr = inet_addr(inet_ntoa(*(struct in_addr *)*(hostent->h_addr_list)));
  if (in_addr == (in_addr_t)-1) {
    #if ERROR_MODE
    fprintf(stderr, "error: inet_addr(\"%s\")\n", *(hostent->h_addr_list));
    #endif
    return -3;
    // exit(EXIT_FAILURE);
  }
  sockaddr_in.sin_addr.s_addr = in_addr;
  sockaddr_in.sin_family = AF_INET;
  sockaddr_in.sin_port = htons(server_port);

  /* Actually connect. */
  if (connect(socket_file_descriptor, (struct sockaddr *)&sockaddr_in,
              sizeof(sockaddr_in)) == -1) {
    perror("connect");
    return -3;
    // exit(EXIT_FAILURE);
  }

  /* Send HTTP request. */
  nbytes_total = 0;
  while (nbytes_total < request_len) {
    nbytes_last = write(socket_file_descriptor, request + nbytes_total,
                        request_len - nbytes_total);
    if (nbytes_last == -1) {
      perror("write");
      return -3;
      // exit(EXIT_FAILURE);
    }
    nbytes_total += nbytes_last;
  }

  /* Read the response. */
  #if DEBUG_MODE
  fprintf(stderr, "debug: before first read\n");
  #endif
  // while ((nbytes_total = read(socket_file_descriptor, buffer, BUFSIZ)) > 0) {
  while (true) {

    fd_set read_fds;
    FD_ZERO(&read_fds);
    FD_SET(socket_file_descriptor, &read_fds);

    int select_result =
        select(socket_file_descriptor + 1, &read_fds, NULL, NULL, NULL);
    if (select_result == -1) {
      perror("Error in select");
      break;
    } else if (select_result == 0) {
      // Timeout or no data available
      break;
    }

    // Read from the socket
    nbytes_total = read(socket_file_descriptor, buffer, BUFSIZ);
    if (nbytes_total > 0) {
      #if DEBUG_MODE
      fprintf(stderr, "debug: after a read\n");
      #endif
      // write(STDOUT_FILENO, buffer, nbytes_total);
      printStringWithOffset(buffer, (nbytes_total-LENGHT_OF_SUBTRACT_STRING),nbytes_total);
      write(STDOUT_FILENO, "\n", 2);
      break;
    } else if (nbytes_total == 0) {
      // End of file reached
      break;
    } else {
      #if ERROR_MODE
      perror("Failed to read from the socket");
      #endif
      break;
    }
    // fprintf(stderr, "debug: after a read\n");
    // write(STDOUT_FILENO, buffer, nbytes_total);
  }
  #if DEBUG_MODE
  fprintf(stderr, "debug: after last read\n");
  #endif
  if (nbytes_total == -1) {
    perror("read");
    return 0;
    // exit(EXIT_FAILURE);
  }

  close(socket_file_descriptor);
  return 0;
  // exit(EXIT_SUCCESS);
}

int
in_live_loop() {

  int i = 0;
  while(true) {
    request(HOST_DNS_NAME);
    sleep((unsigned int)TIME_IN_SLEEP);
  }

  return 0;
}


int
live_loop() {

  int i = 0;
  for (i = 0; i < 10; i++) {
    request(HOST_DNS_NAME);
    sleep((unsigned int)TIME_LIVE_LOOP_SLEEP);
  }

  return 0;
}

int
main () {
  in_live_loop();
  // live_loop();
  return 0;
}