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kill() function problem in client-server ipc message using 2 FIFOs


 
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# 1  
Old 06-10-2011
kill() function problem in client-server ipc message using 2 FIFOs

I want to have a message send & receive through 2 uni-direction FIFO

Flow of data

FIFO1

stdin--->parent(client) writefd--->FIFO1-->child(server) readfd

FIFO2

child(server) writefd2---->FIFO2--->parent(client) readfd2--->stdout

I need to have boundary structed message mesg_len+mesg_type+mesg_data

The function is that if user input "Knock Knock" on stdin, which directs to client, client send this message to server through FIFO1, server compares the string, if matches with "Knock Knock", then server reply message "Who's there?" to client through FIFO2, and client write this message to the stdout.

Last edited by ouou; 06-11-2011 at 04:25 PM..
# 2  
Old 06-10-2011
Quote:
Originally Posted by ouou
I want to have a message send & receive through 2 uni-direction FIFO
Pipes didn't work for ya?
Quote:
I need to have boundary structed message mesg_len+mesg_type+mesg_data
Then pipes don't sound like what you want. Packet sockets would send the exact size of message you want and not buffer.
Quote:
I need help on kill() signals when client types "exit".It seems the client process still live after call kill(). So i have to type ctrl+c to end

The requirement is to terminate all signals,exit program when client type "exit". please help

Please help me. Thanks a lot!
Why do you color everything manually? I can't just quote your message, I have to do work to get rid of that junk.
Code:
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<fcntl.h>
#include<errno.h>
#include<string.h>
#include<sys/wait.h>
#include<sys/types.h>
#include<sys/stat.h>
 
#define MAX_BUF 100
#define MAXMESGDATA (MAX_BUF - 2* sizeof(long))
#define MESGHDRSIZE (sizeof(struct mymesg)-MAXMESGDATA)
#define FIFO1 "/tmp/fifo.1"
#define FIFO2 "/tmp/fifo.2"
#define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)
 
struct mymesg{
long mesg_len; //byte in mesg_data
long mesg_type; //message type
char mesg_data[MAXMESGDATA];
};
 
ssize_t mesg_send (int fd, struct mymesg *mptr){
return (write (fd,mptr,MESGHDRSIZE + mptr->mesg_len));
}
 
ssize_t mesg_recv(int fd,struct mymesg *mptr){
   size_t len;
   ssize_t n;
if ((n=read(fd,mptr,MESGHDRSIZE))==0) {//read hear first, get len of data
return0; //end of file
   } elseif (n!=MESGHDRSIZE){
       printf("message header: expected %d, got %d\n", MESGHDRSIZE,n);
       exit(1);
   }
if ((len=mptr->mesg_len)>0)
   {
if ((n=read(fd,mptr->mesg_data,len))!=len)
       {
           printf("message data: expected %d, got %d\n", len,n);
           exit(1);
       }
   }
return len;
}
 
void client(int readfd,int writefd){
   size_t len;
   ssize_t n;
struct mymesg mesg;
for (;;)
   {
       printf("\nClient:");
       fgets(mesg.mesg_data,MAXMESGDATA,stdin);//read mesg
       len=strlen(mesg.mesg_data);
 
if (mesg.mesg_data[len-1]=='\n') //ignore newline
           len--;
       mesg.mesg_len=len;
       mesg.mesg_type=1;
 
       mesg_send(writefd,&mesg);//write to IPC channel
//read from IPC,write to std output
if((n=mesg_recv(readfd,&mesg))>0)
           write(STDOUT_FILENO,mesg.mesg_data,n);
   }
}
 
void server(int readfd,int writefd){
   ssize_t n;
struct mymesg mesg;
for(;;)
   {
       mesg.mesg_type=1;
//read from IPC channel
if ((n=mesg_recv(readfd,&mesg))==0){
           printf("Message missing");
           exit(1);
       }
 
       mesg.mesg_data[n]='\0';
       mesg.mesg_len=strlen(mesg.mesg_data);
char* str=NULL;
 
if (strcasecmp ("Knock Knock", mesg.mesg_data)==0){
            str="Server:Who's there?";
            strcpy(mesg.mesg_data,str);
            mesg.mesg_len=strlen(str)-1;
           }
elseif(strcasecmp ("Eric", mesg.mesg_data)==0){
           str="Server:Eric,Welcome!";
           strcpy(mesg.mesg_data,str);
           mesg.mesg_len=strlen(str)-1;
           }
elseif(strcasecmp ("Exit", mesg.mesg_data)==0){
           kill(getpid(),SIGTERM); // getpid() gets your OWN pid!
           kill(getppid(),SIGTERM); // After you're dead, you can't kill anything else.
           exit(0);
           }
       mesg_send(writefd,&mesg);
   }
}
 
int main(int argc, char ** argv){
/*MAXMESGDATA== 92 bytes; sizeof(struct mymesg)== 100 bytes 
     2* sizeof(long)== 8 bytes; MESGHDRSIZE ==8 bytes*/
 
int readfd,writefd;
   pid_t childpid;
//create 2 FIFOs
if ((mkfifo(FIFO1,FILE_MODE)<0) && (errno!=EEXIST)){
       printf("can't create %s",FIFO1);
       exit(1);
   }
if ((mkfifo(FIFO2,FILE_MODE)<0) && (errno!=EEXIST)){
       printf("can't create %s",FIFO1);
       unlink(FIFO1);
       exit(1);
   }
if ((childpid=fork()==0)){//child
       readfd=open(FIFO1,O_RDONLY,0);
       writefd=open(FIFO2,O_WRONLY,0);
       server(readfd,writefd);
       exit(0);
   }
//parent
   writefd=open(FIFO1,O_WRONLY,0);
   readfd=open(FIFO2,O_RDONLY,0);
   client(readfd,writefd);
 
   waitpid(childpid,NULL,0);
   close(readfd);
   close(writefd);
   unlink(FIFO1);
   unlink(FIFO2);
return EXIT_SUCCESS;
}

# 3  
Old 06-10-2011
Thanks for your continue help.

I tried this before, just leave the kill (getppid(),SIGTERM) there,it can't terminate the program. in my main(), I put waitpid(childpid,NULL,0);

please help


elseif(strcasecmp ("Exit", mesg.mesg_data)==0){
// kill(getpid(),SIGTERM); // getpid() gets your OWN pid!
kill(getppid(),SIGTERM); // After you're dead, you can't kill anything else.
exit(0);
}

Last edited by ouou; 06-11-2011 at 02:36 PM..
# 4  
Old 06-10-2011
Have you checked the return values of kill()? try perror.

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