Want to Receive dynamic length data from a message queue in IPC?
- by user1089679
Here I have to send and receive dynamic data using a SysV message queue.
so in structure filed i have dynamic memory allocation char * because its size may be varies.
so how can i receive this type of message at receiver side.
Please let me know how can i send dynamic length of data with message queue.
I am getting problem in this i posted my code below.
send.c
/*filename : send.c
*To compile : gcc send.c -o send
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
struct my_msgbuf {
long mtype;
char *mtext;
};
int main(void)
{
struct my_msgbuf buf;
int msqid;
key_t key;
static int count = 0;
char temp[5];
int run = 1;
if ((key = ftok("send.c", 'B')) == -1) {
perror("ftok");
exit(1);
}
printf("send.c Key is = %d\n",key);
if ((msqid = msgget(key, 0644 | IPC_CREAT)) == -1) {
perror("msgget");
exit(1);
}
printf("Enter lines of text, ^D to quit:\n");
buf.mtype = 1; /* we don't really care in this case */
int ret = -1;
while(run) {
count++;
buf.mtext = malloc(50);
strcpy(buf.mtext,"Hi hello test message here");
snprintf(temp, sizeof (temp), "%d",count);
strcat(buf.mtext,temp);
int len = strlen(buf.mtext);
/* ditch newline at end, if it exists */
if (buf.mtext[len-1] == '\n') buf.mtext[len-1] = '\0';
if (msgsnd(msqid, &buf, len+1, IPC_NOWAIT) == -1) /* +1 for '\0' */
perror("msgsnd");
if(count == 100)
run = 0;
usleep(1000000);
}
if (msgctl(msqid, IPC_RMID, NULL) == -1) {
perror("msgctl");
exit(1);
}
return 0;
}
receive.c
/* filename : receive.c
* To compile : gcc receive.c -o receive
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
struct my_msgbuf {
long mtype;
char *mtext;
};
int main(void)
{
struct my_msgbuf buf;
int msqid;
key_t key;
if ((key = ftok("send.c", 'B')) == -1) { /* same key as send.c */
perror("ftok");
exit(1);
}
if ((msqid = msgget(key, 0644)) == -1) { /* connect to the queue */
perror("msgget");
exit(1);
}
printf("test: ready to receive messages, captain.\n");
for(;;) { /* receive never quits! */
buf.mtext = malloc(50);
if (msgrcv(msqid, &buf, 50, 0, 0) == -1) {
perror("msgrcv");
exit(1);
}
printf("test: \"%s\"\n", buf.mtext);
}
return 0;
}
