using serial port read and write

[abdelkader belahcene <abelahcene@gmail.com>]

Hi every body
this is  not for only to debian forum,   since the number of debian'user  is huge
I hope find an answer.
thanks a lot in advance.

I have written 2 small programs for writing on serial port S0   and another for reading from the port S1.
My machines have 2 physical serial port.
I connect the S0 to S1 via   a crossed  cable.

On one machine the programs ran perfectly,
when I tried  them on another machine, exactly same machine running same system ( linuxMint),
in same conditions,  they didn't.


the  writing  program  to port S0  ran     but the reading from S1 !!!   
the situation is like no physical connection on 2 port  exits!!!   It is of course;


Very strange, so may be the   I have to do something to activate    the ports ???
Why it run on one case and not on another!!!

thanks a lot for any idea.
Here are my programs

regards

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/io.h>
#define WAIT  200000
// I have 2 physical serial ports
#define BASEPORT1  0x3f8   
#define BASEPORT2  0x2f8   
int main(){
  char c, i, ch[20], j=0;
  printf("\nPort  S0  OK  \n");
  if (ioperm(BASEPORT2, 3, 1)) {
    printf("\nErrorr S1  \n"); exit(1);
  } 
  if (ioperm(BASEPORT1, 3, 1)) {
    printf("\nError S0  \n"); exit(1);
  }
  printf("\nPort  S1  OK  \n");
  printf("\n\nThis Program must run first !! \n");
  while(1){
    c=inb(BASEPORT2);
    if ( c > 64 && c < 80) break;
    usleep(WAIT);
  }
  printf("\nStart reading from   S1  \n");
  while(j++ <3) {
    for(i=0; i<26 ; i++){
      ch[i]=c;          usleep(WAIT);
      c=inb(BASEPORT2);
    }
    ch[i]=0;// ch[i+1]=0;  
    printf("\nText received %s\n",ch);
  }	
  outb(0, BASEPORT1); // Flush  buffer thru  port S0
  /* We don't need the ports anymore */
  if (ioperm(BASEPORT2, 3, 0)) {perror("ioperm"); exit(1);}  
  exit(0);
}
/****   
This second program    write on S0 port
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/io.h>
#define WAIT  200000
#define BASEPORT1  0x3f8   
#define BASEPORT2  0x2f8   
int main(){
  char c, i, j=0, ch[20];
  /* Get access to the ports */
  if (ioperm(BASEPORT1, 3, 1)) {
    printf("\nError S0 \n"); exit(1);
  }
  printf("\nWriting to   port S0 \n");
  outb(0, BASEPORT1); 
  while(j++ <3)  
    for(c='A'; c<='Z'; c++){
      outb(c, BASEPORT1);
      usleep(WAIT);
    }
  outb(0, BASEPORT1); 
  if (ioperm(BASEPORT1, 3, 0)) {perror("ioperm"); exit(1);}  
  exit(0);
}