/*
Compile: gcc -o fd_server fd_server.c
*/
#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

#define NP1        "/tmp/np1"
#define NP2        "/tmp/np2"
#define MAX_BUF_SIZE    255

int main(int argc, char *argv[])
{
    int rdfd, wrfd, ret_val, count, numread;
    char buf[MAX_BUF_SIZE];

    /* Create the first named - pipe */
    remove(NP1);
    ret_val = mkfifo(NP1, 0666);
    if (ret_val == -1) {
        perror("Error mkfifo(NP1)");
        return 1;
    }
    else
       printf("pipe %s created\n",NP1);

    /* Create the second named - pipe */
    remove(NP2);
    ret_val = mkfifo(NP2, 0666);
    if (ret_val == -1) {
        perror("Error mkfifo(NP2)");
        return 1;
    }
    else
       printf("pipe %s created\n",NP2);

    /* Open the first named pipe for reading */
    if ((rdfd = open(NP1, O_RDONLY)) == -1) {
        perror("Error open(NP1)");
        return 1;
    }
    else
       printf("NP1 opened in read mode FD-%d\n",rdfd);

    /* Open the second named pipe for writing */
    if ((wrfd = open(NP2, O_WRONLY)) == -1) {
        perror("Error open(NP2)");
        return 1;
    }
    else
       printf("NP2 opened in write mode FD-%d\n",wrfd);

    /* Read from the first pipe */
    numread = read(rdfd, buf, MAX_BUF_SIZE);

    buf[numread] = '\0';

    printf("Full Duplex Server : Read From the pipe : %s\n", buf);

    /* Convert to the string to upper case */
    count = 0;
    while (count < numread) {
        buf[count] = toupper(buf[count]);
        count++;
    }

    /* 
     * Write the converted string back to the second 
     * pipe 
     */    
    write(wrfd, buf, strlen(buf));
}

/*
Compile: gcc -o fd_client fd_client.c
*/

#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

#define NP1		"/tmp/np1"
#define NP2		"/tmp/np2"
#define MAX_BUF_SIZE	255

int main(int argc, char *argv[])
{
    int wrfd, rdfd, numread;
    char rdbuf[MAX_BUF_SIZE];

    /* Check if an argument was specified. */

    if (argc != 2) {
        printf("Usage : %s <string to be sent to the server>\n", argv[0]);
        return 1;
    }

    /* Open the first named pipe for writing */
    if ((wrfd = open(NP1, O_WRONLY)) == -1) {
        perror("Error open(NP1)");
        return 1;
    }
    else
       printf("NP1 opened in write mode FD-%d\n",wrfd);

    /* Open the second named pipe for reading */
    if ((rdfd = open(NP2, O_RDONLY)) == -1) {
        perror("Error open(NP2)");
        return 1;
    }
    else
       printf("NP2 opened in read mode FD-%d\n",rdfd);

    /* Write to the pipe */
    write(wrfd, argv[1], strlen(argv[1]));

    /* Read from the pipe */
    numread = read(rdfd, rdbuf, MAX_BUF_SIZE);

    rdbuf[numread] = '\0';

    printf("Full Duplex Client : Read From the Pipe : %s\n", rdbuf);
}