/* internet client                                                  client.c
   compile with       cc client.c -o client
   start the server first
   run with           client <remotehost> <portnumber>   */

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

char *tidyup(char *str)
{ int i,j;
  for (i=0, j=0; str[i]; i++)
  { char c=str[i];
    if (isupper(c)) c=tolower(c);
    if (iscntrl(c)) continue;
    str[j]=c;
    j++; }
  str[j]=0;
  return(str); }

char *getline(FILE *f, char *s, int sz)
{ if (fgets(s,sz,f)==NULL)
  { s[0]=0;
    return(s); }
  tidyup(s);
  return(s); }

void interact(FILE *reader, FILE *writer)
{ int n, command;
  char buffer[10250];

  printf("saying hello to the server...\n");
  fprintf(writer,"hello\n");
  fflush(writer);
  getline(reader,buffer,sizeof(buffer));
  printf("response from the server:\n     \"%s\"\n",buffer);

  while (1)
  { printf("\n");
    printf("Select: 1> Say hello to the server again\n");
    printf("        2> Ask the server what the time is\n");
    printf("        3> Ask the server how it is feeling\n");
    printf("        4> Tell the server to terminate\n");
    printf("        5> Disconnect from the server\n");
    printf("command: ");
    n=scanf("%d",&command);
    if (n==0) continue;

    switch (command)
    { case 1: /* say hello again */
              printf("saying hello to the server...\n");
              fprintf(writer,"hello\n");
              fflush(writer);
              getline(reader,buffer,sizeof(buffer));
              printf("response from the server:\n     \"%s\"\n",buffer);
              break;

      case 2: /* what time is it? */
              printf("asking the server what time it is...\n");
              fprintf(writer,"what time is it?\n");
              fflush(writer);
              getline(reader,buffer,sizeof(buffer));
              if (strstr(buffer,"it is ")==buffer)
              { buffer[30]=0;
                printf("The server said it is now %s.\n",buffer+6); }
              else
                printf("The server made an inappropriate response\n");
              break;

      case 3: /* how are you */
              printf("asking the server how it feels...\n");
              fprintf(writer,"how are you?\n");
              fflush(writer);
              getline(reader,buffer,sizeof(buffer));
              printf("the server replied:\n     \"%s\"\n",buffer);
              break;

      case 4: /* terminate server process */
              printf("telling the server to stop...\n");
              fprintf(writer,"drop dead\n");
              fflush(writer);
              getline(reader,buffer,sizeof(buffer));
              printf("the server replied:\n     \"%s\"\n",buffer);
              break;


      case 5: /* disconect */
              printf("saying goodbye to the server...\n");
              fprintf(writer,"goodbye\n");
              fflush(writer);
              getline(reader,buffer,sizeof(buffer));
              printf("the server responded:\n     \"%s\"\n",buffer);
              break; }
    if (command==5) break; }
  printf("End of interaction.\n"); }

void main(int argc, char *argv[])
{
  char server_name[100];
  int connection,n;
  int port_number;
  struct sockaddr_in server_internet_addr;
  void *sia_ptr=&server_internet_addr;
  int sia_len=sizeof(server_internet_addr);
  struct hostent* server_info_ptr;
  struct in_addr* coded_server_addr;
  FILE *r_file, *w_file;

  if (argc!=3)
  { fprintf(stderr,"usage: %s remote-host port-number\n",argv[0]);
    exit(1); }
  strcpy(server_name,argv[1]);
  n=sscanf(argv[2],"%d",&port_number);
  if (n!=1)
  { fprintf(stderr,"%s: \"%s\" is not a valid port number\n",argv[0],argv[2]);
    exit(1); }

  server_info_ptr=gethostbyname(server_name);
  if (server_info_ptr==NULL)
  { fprintf(stderr,"%s: (1)host \"%s\" not known\n",
            argv[0],server_name); 
    exit(1); }
  coded_server_addr=(struct in_addr*)server_info_ptr->h_addr;
  if ((coded_server_addr->s_addr)==NULL)
  { fprintf(stderr,"%s: (2)host %s not known\n",
            argv[0],inet_ntoa(*coded_server_addr)); 
    exit(1); }

  bzero(sia_ptr,sia_len);
  server_internet_addr.sin_family=AF_INET;
  server_internet_addr.sin_addr.s_addr=coded_server_addr->s_addr;
  server_internet_addr.sin_port=htons(port_number);

  connection=socket(AF_INET,SOCK_STREAM,0);
  if (connection<0)
  { perror("socket failure");
    exit(1); }

  printf("\n[Connecting to %s (%s) on port %d]\n",
          server_name,inet_ntoa(*coded_server_addr),port_number);

  n=connect(connection,sia_ptr,sia_len);
  if (n<0)
  { perror("connect");
    exit(1); }

  r_file=fdopen(connection,"r");
  w_file=fdopen(connection,"w");
  if (r_file==NULL || w_file==NULL)
  { fprintf(stderr,"%s: made a bad connection\n",argv[0]);
    exit(1); }

  interact(r_file, w_file);

  printf("%s: finished\n",argv[0]); }