User2.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <string.h>
#define SERVER 1L
typedef struct {
long msg_to;
long msg_fm;
char buffer[BUFSIZ];
} MESSAGE;
int mid,n;
key_t key;
char buff[50];
struct msqid_ds buf;
MESSAGE msg;
int main(int argc, char** argv) {
//Creating a message queue
key = ftok(".", 'z');
if((mid = msgget(key, IPC_CREAT | 0660))<0){
printf("Error Creating Message Queue\n");
exit(-1);
}
//Display Message Queue and Server ID
printf("Message Queue ID: %d\n", mid);
printf("user2 ID: %ld\n", (long)getpid());
//Receiving message from user1, throws and error if input is invalid
if(msgrcv(mid, &msg, sizeof(msg.buffer), SERVER, 0)<0){
perror("msgrcv");
exit(-1);
}
//user2 displays received message
printf("user2 receives:\n");
printf("%s\n", msg.buffer);
//Aquiring user1 PID to message return
long client = msg.msg_fm;
printf("enter the message to send \n");
scanf("%s",buff);
n=strlen(buff);
for(int i=0;i<=n;i++)
{
msg.buffer[i]=buff[i];
}
//prep return message
msg.msg_fm = SERVER;
msg.msg_to = client;
//send converting message back to client, throws and error if input is invalid
if(msgsnd(mid, (struct MESSAGE*)&msg, sizeof(msg.buffer), 0)==-1){
perror("msgsnd");
exit(-1);
}
//server exits
return (EXIT_SUCCESS);
}