client.c

#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define BUF 1024
#define PORT 6543

int main (int argc, char **argv) {
  int create_socket;
  char buffer[BUF];
  struct sockaddr_in address;
  int size;
  int err = 0;
  char port_to_int[BUF]; //Umwandlung in integer (bei Porteingabe)
  int count; //variable um zum nästen zeichen zu kommen
  int strsize, lines;

  //Eingabe der Argumente ServerIP & Port
  if( argc < 3 ){
             printf("Usage: %s ServerAdresse Port\n", argv[0]);
             exit(EXIT_FAILURE);
      }
  //Port in Integer umwandeln
      strcpy(port_to_int,argv[2]);
      for(count=0;count<(int)strlen(port_to_int);count++)
      {
        if(!isdigit(port_to_int[count]))
        {
            err++;
        }
     }
     if(err > 0)
      {
        printf("Nur Zahlen beim Port eingeben\n");
        exit(EXIT_FAILURE);
      }
      //PORT = atoi(port_to_int);

  //Socket oeffnen
  if ((create_socket = socket (AF_INET, SOCK_STREAM, 0)) == -1)
  {
     perror("Socket error");
     return EXIT_FAILURE;
  }
  //Serveradresse initialisieren
  memset(&address,0,sizeof(address));
  address.sin_family = AF_INET;
  address.sin_port = htons (PORT);
  inet_aton (argv[1], &address.sin_addr);

  //Verbinden
  if (connect ( create_socket, (struct sockaddr *) &address, sizeof (address)) == 0)
  {
     printf ("Erfolgreich mit Server %s verbunden. Port: %d\n", inet_ntoa (address.sin_addr), PORT);
     size=recv(create_socket,buffer,BUF-1, 0);
     if (size>0)
     {
        buffer[size]= '\0';
        printf("%s",buffer);
     }
  }
  else
  {
     perror("Connect error - no server available");
     return EXIT_FAILURE;
  }

  do {
     //printf ("Send message: ");
     fgets (buffer, BUF, stdin);

    if(strcmp(buffer,"LIST\n") == 0)
    {
        //LIST Befehl an server üagen
        send(create_socket, buffer, strlen (buffer), 0);
        //Antwort vom Server
        size = recv(create_socket, &lines, sizeof(int), 0);

        if (size < 4)
            lines = 0;

        for (; lines; --lines)
        {
            size = recv(create_socket, &strsize, sizeof(strsize), 0);
            if (size > 0)
            {
                size=recv(create_socket,buffer,strsize, 0);
                if (size>0)
                {
                    buffer[size] = '\0';
                   printf("%s", buffer);
                }
            }
         }
    }
    else if(strcmp(buffer,"GET\n") == 0)
    {
        //GET command to the server
        send(create_socket, buffer, strlen (buffer), 0);

         }
    else
    {
        printf("Es werden nur folgende Befehle erkannt: LIST, GET und QUIT\nBitte erneut versuchen\n");
    }
  }while (strcmp (buffer, "QUIT\n") != 0);
  close (create_socket);
  return EXIT_SUCCESS;
}