Message queue for interprocess communication

establish server.c and client.c, The client is responsible for entering two operands and an operator , The server is responsible for receiving and calculating the two operands according to the operator , Finally, the operation result is returned to the client for output . Such as client input 2+4, The server will send the result 6 Return to the client .

Their thinking ：

The purpose of this topic is to investigate how to use the related functions of message queue. The client and server can be understood as the sender and receiver respectively, so we only need to create a message queue , Every time the client passes into the message queue 3 It's worth , They are calculated numbers and operation symbols , The server only needs to process and convert the received value , I am dealing with this problem is , There is not much research on the incoming information of message queue , Instead, I think the main problem is how to convert the received message into operands and symbols .

tips: The code is rough , But the basic functions can be realized . If you have more ideas , You can write in the comments section . Accept your correction and criticism .

Code implementation

client

#include<stdio.h>
#include<string.h>
#include<unistd.h>
#include<sys/ipc.h>
#include<sys/msg.h>
#include<time.h>
#include<sys/types.h>
struct msgbuf
{
   long mtype;
   char mtext[500];
};
int main()
{
	int msqid;
	int msqid1;
	int i;
	struct msgbuf buf;
	int flag;
	int sendlength;
	msqid = msgget((key_t)1111 , IPC_CREAT|0666);
	if(msqid<0)
	printf("ERROR");
	
	buf.mtype = 1;
	sendlength = sizeof(struct msgbuf) - sizeof(long);
	sprintf(buf.mtext,"Hello World");
	msgsnd(msqid,&buf,sendlength,0);
	msgrcv(msqid,&buf,sendlength,1,0);
	printf("%s",buf.mtext);
	for(i = 0 ; i<3;i++)
	{
	scanf("%s",buf.mtext);
	flag = msgsnd(msqid,&buf,sendlength,0);
	if(i == 3)
	break;
	}
	

	


	return  0;
}

The server

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<sys/ipc.h>
#include<sys/msg.h>
#include<time.h>
#include<sys/types.h>
struct msgbuf
{
   long mtype;
   char mtext[500]; 
};
int main()
{
	int msqid;
	int msqid1;
	struct msgbuf buf;
	int flag;
	int number1,number2,sum,i;
	char *a;
	int recvlength;
	msqid = msgget(1111 , 0);
	if(msqid<0)
	printf("ERROR");
	buf.mtype = 1;
	recvlength = sizeof(struct msgbuf) - sizeof(long);
	for(i=0;i<3;i++)
	{
	flag = msgrcv(msqid,&buf,recvlength,1,0);
	if(i==0)
	{
	number1 = atoi(buf.mtext);
	printf("%d\n",number1);
	}
	else if(i==1)
	{
	number2 = atoi(buf.mtext);
	printf("%d\n",number2);
	}
	else if(i == 2)
	{
	  a = buf.mtext;
	  printf("%s\n",a);
	}
	}
	  if(strcmp(a, "*") == 0)
	  printf("%d\n",i = number1*number2);
	  else if(strcmp(a, "/") == 0)
	  printf("%d\n",i=number1/number2);
	  else if(strcmp(a, "+") == 0)
	  printf("%d\n",i=number1+number2);
	  else if(strcmp(a, "-") == 0)
	  printf("%d\n",i=number1-number2);
	  else
	  printf("ERROR!!!\n");
	  sprintf(buf.mtext,"%d",i);
	  msgsnd(msqid,&buf,recvlength,0);
	  printf("OVER\n");
	return  0;
}

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