Blank msgrcv buffer - c

Question

I tried to run the message queue program of a telephonic conversation between a caller and a receiver given here with the correction stated.I keep getting the following result:
./caller
Caller Program
<<<
CALLER:Hello!!
while running the caller executable.The message buffer while receiving is empty.I don't know why.Please help!!
The caller.c is:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <pthread.h>
struct msgbuf
{
long mtype;
char mtext[140];
}msg_buf;
int send_msg_id,receive_msg_id;
key_t send_key,receive_key;
void *send_message(void *a)
{
send_key=ftok("Caller1.c",'A');
if (send_key==-1)
{
printf("\nCaller send key error");
exit(1);
}
send_msg_id=msgget(send_key,0666 | IPC_CREAT);
if (send_msg_id==-1)
{
printf("\nCaller send msgget error");
exit(1);
}
printf("\nCALLER:");
while (fgets(msg_buf.mtext,sizeof(msg_buf.mtext),stdin)!=NULL)
{
msg_buf.mtype=1;
int len=strlen(msg_buf.mtext);
if (msg_buf.mtext[len-1]=='\n');
msg_buf.mtext[len-1]='\0';
if (msgsnd(send_msg_id,&msg_buf,len+1,0)==-1)
printf("\nMsg sending error\n");
}
int i=0;
while(i<9999)
i++;
msgctl(send_msg_id,IPC_RMID,NULL);
return;
}
void *receive_message(void *a)
{
receive_key=ftok("Receiver1.c",'B');
if (receive_key==-1)
{
printf("\nReceiver send key error");
exit(1);
}
send_msg_id=msgget(receive_key,0777|IPC_CREAT);
if (receive_msg_id==-1)
{
printf("\nCaller msgrcv error");
exit(1);
}
printf("\n<<<");
while(1)
{
if(msgrcv(receive_msg_id,&msg_buf,sizeof(msg_buf.mtext),1,0)!=-1)
printf("<<<%s\n",msg_buf.mtext);
}
return;
}
void initialize()
{
pthread_t send_thread,receive_thread;
pthread_create(&send_thread,NULL,send_message,NULL);
pthread_create(&receive_thread,NULL,receive_message,NULL);
pthread_join(send_thread,NULL);
pthread_join(receive_thread,NULL);
return;
}
int main()
{
printf("\nCaller Program\n");
initialize();
return 0;
}