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TCP/IP komunikácia (server/klient) v OS Linux

Úvod

IP

TCP

TCP/IP komunikácia

Protokol TCP/IP

UDP

Socket

Resolve Domain Name

/* resolve_domain_name */

#include <stdio.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
  struct hostent *host;
  char **aliases;
  register int i;

  /* osetrenie poctu argumentov */	
  if (argc != 2) {
    printf("Pouzitie:  %s domain_name\n", argv[0]);
    printf("Napríklad: %s localhost\n", argv[0]);
    return(-1);
  }

  /* osetrenie existencie adresy (domain_name) */
  if (!(host=gethostbyname(argv[1]))) {
    printf("Chyba: nepodarilo sa najst %s\n", argv[1]);
    return(-1);
  }

  /* udaje o stroji s adresou domain_name */
  printf("Meno: %s\n", host->h_name);
  
  printf("Aliasy:");
  aliases=host->h_aliases;
  while (*aliases) {
    printf(" %s", *(aliases++));
  }
  
  i=0;
  printf("\nIP adresy:");
  while (host->h_addr_list[i]) {
    /* inet_ntoa() prevod do "bodkoveho" tvaru */	  
    printf(" %s", inet_ntoa(*(struct in_addr *)host->h_addr_list[i++]));
  }
  
  printf("\nPocet IP adries: %i\n", i);
  printf("Velkost IP adries: %iB\n", host->h_length);

  return 0;
}

Klávesnica v konzole

/* void init_kbhit(void) inicializuje kbhit */
/* int kbhit(void) vracia ascii kod stlacenej klavesy alebo nulu ak nebolo nic stlacene */
/* void close_kbhit(void) konci pracu s kbhit */

#include <termios.h>
#include <term.h>
#include <curses.h>

/* deklaracia struktur pre nastavenie terminalu */
struct termios initial_settings;
struct termios new_settings;
/* premenna pre detekciu stlacenej klavesy */
int peek_character=-1;

/*******************************/
int kbhit(void)
{
  int key=0;
 
  if (kbhit_on()) key=readkey_on();
  return(key);
}  

/*******************************/
void init_kbhit(void)
{
  tcgetattr(0, &initial_settings);
  new_settings=initial_settings;
  new_settings.c_lflag &= ~ICANON;
  new_settings.c_lflag &= ~ECHO;
  new_settings.c_lflag &= ~ISIG;
  new_settings.c_cc[VMIN]=1;
  new_settings.c_cc[VTIME]=0;
  tcsetattr(0, TCSANOW, &new_settings);
}

/*******************************/
void close_kbhit(void)
{
  tcsetattr(0, TCSANOW, &initial_settings);
}


int kbhit_on(void)
{
  char ch;
  int nread;

  if (peek_character != -1) return(1);
  
  new_settings.c_cc[VMIN]=0;
  tcsetattr(0, TCSANOW, &new_settings);
  nread=read(0, &ch, 1);
  new_settings.c_cc[VMIN]=1;
  tcsetattr(0, TCSANOW, &new_settings);
   
  if (nread==1) {
    peek_character=ch;
    return(1);
  }

  return(0);
}


int readkey_on(void)
{
  char ch;

  if (peek_character!=-1) {
    ch=peek_character;
    peek_character=-1;
    return(ch);
  }

  read(0, &ch, 1);
  return(ch);
}

TCP/IP Client

/* test_tcp_client */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>
#include "kbhit.c"

#define SIZEMSG 1024

extern int errno;
extern int h_errno;

int main(int argc, char *argv[])
{
  char recv_msg[SIZEMSG];         // prijata sprava
  char send_msg[SIZEMSG];         // odoslana sprava
  struct hostent *server_host;    // struct servera
  struct sockaddr_in server_sock; // struct serveroveho socketu
  int my_sock_fd ;                // file deskriptor mojho client socketu
  int server_port;                // cislo portu
  int count_byte;                 // pocet prijatych a odoslanych byte
  int i;
  int key=0;                      // stlacena klavesa (kbhit)

  system("clear");
  printf("TCP/IP socketova komunikacia [CLIENT]\n");
  system("date");
  printf("\n");

  /* osetrenie poctu argumentov */
  if (argc != 3) {
    printf("Pouzitie:  %s adresa_servera port_servera\n", argv[0]);
    printf("Napriklad: %s localhost 1024\n\n", argv[0]);
    return(-1);
  }

 /* osetrenie existencie adresy servera (domain_name) a vypis infa o nom */
  if (!(server_host=gethostbyname(argv[1]))) {
    printf("Chyba: Nepodarilo sa najst server %s [%i]\n", argv[1], h_errno);
    herror("Chyba"); // textovy vypis chyby h_errno
    switch (h_errno) {
      case HOST_NOT_FOUND: 
        printf("       Specifikovaný server je neznamy [HOST_NOT_FOUND]\n");
        break;
      case NO_ADDRESS: 
        printf("       Meno servera je platne, ale nema ziadnu IP adresu [NO_ADDRESS]\n"); 
        break;
      case NO_RECOVERY: 
        printf("       Neodstranitelna chyba menneho servera [NO_RECOVERY]\n");
        break;
      case TRY_AGAIN: 
        printf("       Docasna chyba menneho servera [TRY_AGAIN]\n"); 
        break;
      default:
	printf("       Radsej sa chod prejst po lese\n");
	break;
    }
    printf("\n");
    return(-1);
  }
  printf("... server %s najdeny [OK]\n", argv[1]);
  printf("    meno servera: %s\n", server_host->h_name);
  i=0;
  printf("    IP adresa servera:");
  while (server_host->h_addr_list[i]) {
    /* inet_ntoa() prevod do "bodkoveho" tvaru */
    printf(" %s", inet_ntoa(*(struct in_addr *)server_host->h_addr_list[i++]));
  }
  printf("\n\n");

  /* vytvorenie mojho lokalneho client socketu (socket) */
  if ((my_sock_fd=socket(AF_INET, SOCK_STREAM, IPPROTO_TCP))==-1) {
    printf("Chyba: nepodarilo sa vytvorit socket\n\n");
    return(-1);
  }
  printf("... socket [%i] vytvoreny [OK]\n\n", my_sock_fd);

  /* naplnenie struktury server_sock (sockaddr_in) */
  server_port = atoi(argv[2]);
  server_sock.sin_family = AF_INET; // rodina protokolu
  server_sock.sin_port = htons(server_port); // cislo portu na serveri
  // IP adresa servera ako kopia polozky struktury server_host
  memcpy(&(server_sock.sin_addr), server_host->h_addr, server_host->h_length);

  /* pripojenie (connect) */
  if (connect(my_sock_fd, (struct sockaddr *)&server_sock, sizeof(server_sock))==-1) {
    printf("Chyba: nepodarilo sa  naviazat spojenie so serverom %s [%i]\n", argv[1], errno);
    herror("Chyba"); // textovy vypis chyby errno
    switch (errno) {
      case EBADF: 
        printf("       Zly deskriptor socketu [EBADF]\n");
	break;
      case EFAULT: 
        printf("       Adresa socketu je mimo adresovy priestor procesu [EFAULT]\n"); 
        break;
      case ENOTSOCK: 
        printf("       Deskriptor nie je platnym deskriptorom socketu [ENOTSOCK]\n"); 
        break;
      case EISCONN: 
        printf("       Socket je uz spojeny [EISCONN]\n");
       	break;
      case ECONNREFUSED: 
        printf("       Spojeníe bolo odmietnute serverom [ECONNREFUSED]\n");
       	break;
      case ETIMEDOUT: 
        printf("       Casovy limit pre spojenie vyprsal [ETIMEDOUT]\n");
       	break;
      case ENETUNREACH: 
        printf("       Síet nie je dosiahnutelna [ENETUNREACH]\n");
       	break;
      case EADDRINUSE: 
        printf("       Adresa je uz pouzivana [EADDRINUSE]\n");
       	break;
      default: 
	printf("       Radsej sa chod prejst po lese\n");
	break;
    }
    printf("\n");
    return(-1);
  }
  printf("... spojenie so serverom naviazane [OK]\n\n");

  /* ---------------------------------------------------------------- */

  printf("[q]-quit (ukoncenie klienta)\n[s]-send (posli spravu serveru)\n\n");
  init_kbhit();

  /* cyklus odosielania a prijimania sprav */
  while (key!='q') {
    key=kbhit();
    if (key=='s') {
      strcpy(send_msg, "");
      /* nacitanie spravy z klavesnice */
      printf("<send> ");
      close_kbhit();
      fgets(send_msg, SIZEMSG, stdin);
      // printf("\n");
      init_kbhit();
      /* odoslanie spravy (send) */
      count_byte=0;
      if ((count_byte=send(my_sock_fd, send_msg, SIZEMSG, 0))==-1) {
        printf("Chyba: nepodarilo sa odoslat spravu\n\n");
      }
    }
    
    /* prijem spravy (recv) */
    strcpy(recv_msg, "");
    count_byte=0;
    if ((count_byte=recv(my_sock_fd, recv_msg, SIZEMSG, MSG_DONTWAIT))>0) {
      printf("\a<recv> %s", recv_msg);
      // printf("\n\n");
    }  

  } // koniec whileho
    
  /* uzatvorenie spojenia (close) */
  close_kbhit();  
  close(my_sock_fd);
  printf("\n... socket uzatvoreny [OK]\n");
  printf("... spojenie ukoncene [OK]\n");
  printf("... cinnost klienta ukoncena [OK]\n\n");
    
  return(0);
}

TCP/IP Server

/* test_tcp_server */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include "kbhit.c"

#define SIZEMSG 1024
#define SIZEFRONT 1

extern int h_errno;

int main(int argc, char *argv[])
{
  char recv_msg[SIZEMSG];         // prijata sprava
  char send_msg[SIZEMSG];         // odoslana sprava
  struct sockaddr_in server_sock; // struct serveroveho socketu
  struct sockaddr_in client_sock; // struct klientskeho socketu
  socklen_t client_len;           // dlzka adresy klienta
  int server_port;                // cislo portu
  int my_sock_fd;                 // file deskriptor mojho server socketu
  int client_sock_fd;             // file deskriptor klientskeho socketu
  int count_byte;                 // pocet prijatych a odoslanych byte
  int key=0;                      // stlacena klavesa (kbhit)
  
  unlink("server_socket");
  system("clear");
  printf("TCP/IP socketova komunikacia [SERVER]\n");
  system("date");
  printf("\n");

  /* osetrenie poctu argumentov */
  if (argc != 2) {
    printf("Pouzitie:  %s port_servera\n", argv[0]);
    printf("Napriklad: %s 1024\n\n", argv[0]);
    return(-1);
  }

  /* vytvorenie mojho lokalneho server socketu (socket) */
  if ((my_sock_fd=socket(AF_INET, SOCK_STREAM, IPPROTO_TCP))==-1) {
    printf("Chyba: nepodarilo sa vytvorit socket\n\n");
    return(-1);
  }
  printf("... socket [%i] vytvoreny [OK]\n\n", my_sock_fd);

  /* naplnenie struktury server_sock (sockaddr_in) */
  server_port = atoi(argv[1]);
  server_sock.sin_family = AF_INET; // rodina protokolu
  server_sock.sin_port = htons(server_port); // cislo portu na serveri
  server_sock.sin_addr.s_addr = INADDR_ANY; // moze sa pripojit kazdy (INADDR_ANY)

  /* pomenovanie socketu (bind) */
  if (bind(my_sock_fd, (struct sockaddr *)&server_sock, sizeof(server_sock))==-1) {
    printf("Chyba: nepodarilo sa pomenovat socket\n\n");
    return(-1);
  }
  printf("... socket [%i] pomenovany [OK]\n\n", my_sock_fd);
  
  /* vytvorenie fronty ziadosti o pripojenie (listen) */ 
  if (listen(my_sock_fd, SIZEFRONT)==-1) {
    printf("Chyba: nepodarilo sa vytvorit frontu ziadosti o pripojenie\n\n");
    return(-1);
  }
  printf("... fronta ziadosti o pripojenie vytvorena [OK]\n\n");
  
  /* prijatie klienta (accept) */
  client_len=sizeof(client_sock);
  if ((client_sock_fd=accept(my_sock_fd, (struct sockaddr *)&client_sock, &client_len))==-1) {
    printf("Chyba: nepodarilo sa akceptovat ziadost o pripojenie");
    return(-1);
  }
  printf("... ziadost o pripojenie akceptovana [OK]\n");
  printf("    IP adresa klienta: %s\n", inet_ntoa((struct in_addr)client_sock.sin_addr));
  printf("    spojenie so serverom naviazane [OK]\n\n");

  /* ---------------------------------------------------------------- */

  printf("[q]-quit (ukoncenie servera)\n[s]-send (posli spravu klientovi)\n\n");
  init_kbhit();

  /* cyklus odosielania a prijimania sprav */
  while (key!='q') {
    key=kbhit();
    if (key=='s') {
      strcpy(send_msg, "");
      /* nacitanie spravy z klavesnice */
      printf("<send> ");
      close_kbhit();
      fgets(send_msg, SIZEMSG, stdin);
      // printf("\n");
      init_kbhit();
      /* odoslanie spravy (send) */
      count_byte=0;
      if ((count_byte=send(client_sock_fd, send_msg, SIZEMSG, 0))==-1) {
        printf("Chyba: nepodarilo sa odoslat spravu\n\n");
      }
    }
    
    /* prijem spravy (recv) */
    strcpy(recv_msg, "");
    count_byte=0;
    if ((count_byte=recv(client_sock_fd, recv_msg, SIZEMSG, MSG_DONTWAIT))>0) {
      printf("\a<recv> %s", recv_msg);
      // printf("\n\n);
    }  

  } // koniec whileho
 
  /* uzatvorenie spojenia (close) */
  close_kbhit();
  close(my_sock_fd);
  close(client_sock_fd);
  printf("\n... socket uzatvoreny [OK]\n");
  printf("... spojenie ukoncene [OK]\n");
  printf("... cinnost servera ukoncena [OK]\n\n");
 
  return(0);
}

Manuálové stránky

Download

Záver

Zdroje

• manuálové stránky (RedHat 7.3)
• Neil Mathew, Richard Stones - Linux Začínáme programovat
• seriál článkov o socketoch na http://www.builder.cz
• Príručka správcu siete pre školy podporované projektom Infovek (LŠOG Zvolen 2002)