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Full Discussion: Message Queue Problem
Top Forums Programming Message Queue Problem Post 70547 by SaTYR on Sunday 1st of May 2005 03:07:59 AM
Old 05-01-2005
Network Message Queue Problem

Hi all,

I need help about message queues, i have a server-client program that communicates each other via msg queue, firstly server opens its msg queue and waits for msg then client opens server msg queue and its own msg queue(for receiving msg from server,clients sends msg to server msg queue,but receives their reply from their private msg queue).
I have problem at sending generated structure to the server Smilie...

I am also sending my source code for help..

Code:
//Here is my client source
#define MAXLEN 32	
#define MSGKEY	5L

typedef struct my1_msgbuf
{
        int receiver_id;  //server msg queue
	int sender_id;  //client msg queue
        char message[MAXLEN]; //msg to server
}my_msgbuf;

void main (int argc, char *argv[])
{
        my_msgbuf 	buffer;
        int		msgID;
	int myId;


        if (argc<2)
        {
                printf("Give message as parameter!");
                exit(-1);
        }

        //create and get a message queue
        if ((msgID=msgget(MSGKEY,0666|IPC_CREAT))<0)
        {
                perror("Error getting msg queue.");
                exit(-1);
        }

	if((myId=msgget(112233,0666|IPC_CREAT))<0){//create client msgq-im just testing with 112233
		perror("Error getting client msg queue!\n");
		exit(-2);
	}

        //copy the message into the buffer (prepare)
        strcpy(buffer.message,argv[1]);
        buffer.receiver_id=msgID; //server msgq id
	buffer.sender_id=myId;//client msg q id - server need to know client id

        //send the message to the OS-managed buffer
        if (msgsnd(msgID,&buffer,sizeof(buffer.message),0)<0)//here i have an invalid argument exception!!!
        {
                perror("Error writing to message queue.");
                exit(-1);
        }

        printf("Message has been send.\n\n");
	//wait msg from server
	if(msgrcv(myId,&buffer,sizeof(buffer),0L,0)<0){//waiting server to reply me..
		printf("Unable to receive client msg\n.");
		exit(1);
	}

        exit(0);
}

//Here is the server side
define MAXLEN	256
#define MSGKEY	5L

typedef struct my1_msgbuf
{
	int receiver_id;
        int sender_id;
        char message[MAXLEN];
}my_msgbuf;

void main ()
{
        my_msgbuf 	buffer;
        int		msgID;
	int temp;

        //create and get a message queue
        if ((msgID=msgget(MSGKEY,0666|IPC_CREAT))<0)
        {
                perror("Error getting msg queue.");
                exit(-1);
        }

        //RECEIVE MESSAGE FROM OPERATING SYSTEMS QUEUE

        if (msgrcv(msgID,&buffer,
        sizeof(buffer.message),0L,0)<0)
        {
                perror("Error receiving message from Queue.");
                exit(-1);
        }

        printf("\nMessage read from queue:\n\n");
        printf("MESSAGE: %s\n",buffer.message);
	printf("Sender id: %d\n",buffer.sender_id);
	printf("Receiver id: %d\n",buffer.receiver_id);

	temp = buffer.receiver_id;
	buffer.receiver_id = buffer.sender_id;
	buffer.sender_id = temp;

	//Send same msg to the client that send..
while(msgsnd(buffer.receiver_id,&buffer,sizeof(buffer),0)>0);

        //DELETE QUEUE

        if (msgctl(msgID,IPC_RMID,0)<0)
        {
                perror("Error deleting message queue.");
                exit(-1);
        }

        exit(0);
}

What is the problem here?
Thanks.
 

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msg.h(3HEAD)							      Headers							      msg.h(3HEAD)

NAME
msg.h, msg - message queue structures SYNOPSIS
#include <sys/msg.h> DESCRIPTION
The <sys/msg.h> header defines the following data types through typedef: msgqnum_t used for the number of messages in the message queue msglen_t used for the number of bytes allowed in the message queue These types are unsigned integer types that are able to store values at least as large as a type unsigned short. The <sys/msg.h> header defines the following constant as a message operation flag: MSG_NOERROR no error if big message The msqid_ds structure contains the following members: struct ipc_perm msg_perm Operation permission structure. msgqnum_t msg_qnum Number of messages currently on queue. msglen_t msg_qbytes Maximum number of bytes allowed on queue. pid_t msg_lspid Process ID of last msgsnd(2). pid_t msg_lrpid Process ID of last msgrcv(2). time_t msg_stime Time of last msgsnd(). time_t msg_rtime Time of last msgrcv(). time_t msg_ctime Time of last change. The pid_t, time_t, key_t, size_t, and ssize_t types are defined as described in <sys/types.h>. See types(3HEAD). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
msgctl(2), msgget(2), msgrcv(2), msgsnd(2), ipc.h(3HEAD), types.h(3HEAD), attributes(5), standards(5) SunOS 5.10 10 Sep 2004 msg.h(3HEAD)
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