Creare una applicazione client server per Linux/Unix [mod]

Devo realizzare una semplice applicazione client server in c sotto unix/linux.
Due semplici file uno client e uno server.
Avete qualche idea ?

[binarysun]

Dipende da che devi fare!

Sposto nella sezione adatta...

[pietrovischia]

Anni fa ho smanettato ricalcando un tutorial che avevo trovato in giro, non ricordo dove purtroppo

Posto qui il codice: è un minicoso che permette di mandare stringhe di caratteri. Se non ricordo male, funzionava.
Datti una occhiata e modifica il tutto per arrivare alle features di cui necessiti, e lascia stare le menate sulla gnu
Non ricordo se è gia' supportata la multiconnessione di piu' utenti, comunque in teoria non dovrebbe essere troppo laborioso. In teoria.
CLIENT

/* This code is Copyrighted (C) 2002 by Pietro Vischia.
 * Released under the terms of the GNU General Public License.
 * If you modify my code, please send me a copy of the new code,
 * so I will check the weaknesses of my code.
 * mailto: shadow_shark@libero.it
 *
 * This file is part of SOCK_EX 0.1.
 *
 *   SOCK_EX 0.1 is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   SOCK_EX 0.1 is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with SOCK_EX 0.1; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA  */


/* This is a very simple client which establish a TCP connection
 * with a remote server and sends to it a string of characters.
 * It doesn't support DNS lookup yet.
 * Data-encapsulating in defined-size packets is not implemented yet.
 */

/* To do: implementing reading-buffer and sending-buffer, for sending message more of 128 byte long dividing them into 128-bytes-long packets */

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

/* Max packet size set to 128 byte */
#define MAX_DATA_SIZE 128

int main(int argc, char *argv[]){
  
  short int port;
  /* Message is stored in a 128-byte array. */
  char buf[MAX_DATA_SIZE];
  int main_fd;
  struct sockaddr_in server_address;
  
  /* Control on startup syntax */
  if(argc!=3){
    printf("Usage: client hostname port\n");
    exit(1);
  }
  
  /* Convert string into short integer for port number */
  port = atoi(argv[2]);
  
  printf("Please insert the message you would like to send:\n");
  
  /* Control on data input */
  if(fgets(buf, MAX_DATA_SIZE-1, stdin) == NULL){
    perror("Error reading data from standard input");
    exit(1);
  }
  
  /* Control on socket file descriptor creation */
  if((main_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
    perror("Error starting up socket file descriptor");
    exit(1);
  }
  
  server_address.sin_family      = AF_INET;
  server_address.sin_port        = htons(port);
  server_address.sin_addr.s_addr = inet_addr(argv[1]);
  memset (&(server_address.sin_zero), '\0', 8);
  
  /* Control on establishing connection with remote host */
  if(connect(main_fd, (struct sockaddr *)&server_address, sizeof(struct sockaddr)) == -1){
    perror("Error connecting to remote host");
    exit(1);
  }
  
  /* Control on data transmission */
  if(send(main_fd, buf, sizeof(buf) , 0) == -1){
    perror("Error sending message");
    exit(1);
  }
  printf("Message sent\n");
  buf[MAX_DATA_SIZE] = '\0';
  
  close(main_fd);
  return(0);
}

SERVER:

/* This code is Copyrighted (C) 2002 by Pietro Vischia
 * Released under the terms of the GNU General Public License.
 * If you modify my code, please send me a copy of the new code,
 * so I will check the weaknesses of my code
 *
 * This file is part of SOCK_EX 0.1.
 *
 *   SOCK_EX 0.1 is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   SOCK_EX 0.1 is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with SOCK_EX 0.1; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/* This is a very simple server which accepts some TCP
 * connections from a remote client and print on screen
 * the received data.
 * It doesn't allow listening on a port below 1024, so it
 * can be safely used from a non-superuser account.
 * Encapsulating data in defined-size packets is not implemented yet.
 */

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

/* Allow 15 simultaneous connections to specified port */
#define BACKLOG 15

/* Max packet size set to 128 byte */
#define MAX_DATA_SIZE 128

int main (int argc, char *argv[]){
  
  short int port;
  int main_fd;
  struct sockaddr_in server_address;
  int sin_size;
  struct sockaddr_in client_address;
  int connection_fd;
  char buf[MAX_DATA_SIZE];
  
  /* Control on startup syntax */
  if(argc != 2) {
    printf("Usage: server port");
    exit(1);
  }
    
  /* Convert string into short integer for port number */
  port = atoi(argv[1]);
  
  /* Control on non-allowed ports */
  if(port <= 1024){
    printf("Ports below 1024 are reserved, unless you are SysAdmin.\nSearch http://shadow_shark.tripod.com for the SysAdmin version of this server\n");
    exit(1);
  }
  
  /* Control on socket file descriptor creation */
  if((main_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
    perror("Error starting up socket file descriptor");
    exit(1);
  }
  
  /* Waiting if the port is in use is not implemented yet */

  /* Defining address of host in which server is running */
  server_address.sin_family      = AF_INET;
  server_address.sin_port        = htons(port);
  server_address.sin_addr.s_addr = htonl(INADDR_ANY);
  memset(&(server_address.sin_zero), '0', 8);
  
  /* Control on binding to specified port */
  if(bind(main_fd, (struct sockaddr *)&server_address, sizeof(struct sockaddr)) == -1){
    perror("Error binding server to specified port");
    exit(1);
  }
  
  /* Control on listening on specified port */
  if(listen(main_fd, BACKLOG) == -1){
    perror("Error listening on specified port");
    exit(1);
  }
  
  /* Code for elimination of zombie processes is not implemented yet */
  
  /* Main connection loop */
  while(1){
    sin_size = sizeof(struct sockaddr_in);
    
    /* Control on accepting connections from a remote client */
    if((connection_fd = accept(main_fd, (struct sockaddr *)&client_address, &sin_size)) == -1){
      perror("Error accepting connection");
      exit(1);
    }
    
    printf("Message from server: finally I got a connection from %s\n\n", inet_ntoa(client_address.sin_addr));
    
    /* Creating child file descriptor for new connection (main_fd continue listening on port) */
    if(!fork()){
      close(main_fd);
      
      /* Control on receiving data. A better definition of packets size and a full control
	 on receiving packets are not implemented yet. */
      if(recv(connection_fd, buf, MAX_DATA_SIZE, 0) == -1){
	perror("Error receiving data from client");
	exit(1);
      }
      printf("Message:\n%s\n", &buf);
      close(connection_fd);
      exit(0);
    }
    /* Why another time? */
    close(connection_fd);
  }
  return(0);
}

basta impararsi le socket...