进程间通信之消息队列

消息队列由操作系统提供，一个进程向另一个进程发送有类型数据块。

生命周期：随内核。

消息队列的实现：

comm.h:
#ifndef _COMM_H_
#define _COMM_H_
#include<stdio.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/msg.h>
#include<string.h>
#define PATHNAME "."
#define PROJ_ID 0x6666
#define SERVER_TYPE 1
#define CLIENT_TYPE 2
#define SIZE 128
struct msgbuf
{
    long mtype;
    char mtext[SIZE];
};
int createMsgQueue();
int getMsgQueue();
int sendMsg(int msgid,long type,const char* msg);
int recvMsg(int msgid,long type,char out[]);
int destroyMsgQueue(int);
#endif
comm.c:
#include "comm.h"
int commMsgQueue(int flag)
{
    key_t k=ftok(PATHNAME,PROJ_ID);
    if(k<0)
    {
        perror("ftok");
        return -1;
    }
    //int msg_id = msgget(k,IPC_CREAT|IPC_EXCL|0666);
    int msg_id = msgget(k,flag);
    if(msg_id<0)
    {
        perror("msgget");
        return -2;
    }
    return msg_id;
}
int createMsgQueue()
{
    return commMsgQueue(IPC_CREAT|IPC_EXCL|0666);
}
int getMsgQueue()
{
    return commMsgQueue(IPC_CREAT);
}
int sendMsg(int msgid,long type,const char* info)
{
    struct msgbuf msg;
    msg.mtype=type;
    strcpy(msg.mtext,info);
    if(msgsnd(msgid,&msg,sizeof(msg.mtext),0)<0)
    {
        perror("msgsnd");
        return -1;
    }
    return 0;
}
int recvMsg(int msgid,long type,char out[])
{
    struct msgbuf msg;
    if(msgrcv(msgid,&msg,sizeof(msg.mtext),type,0)<0)
    {
        perror("msgrcv");
        return -1;
    }
    strcpy(out,msg.mtext);
    return 0;
}
int destroyMsgQueue(int msgid)
{
    if(msgctl(msgid,IPC_RMID ,NULL)<0)
    {
        perror("msgctl");
        return -3;
    }
    return 0;
}
server.c:
#include "comm.h"
int main()
{
    int msgid = createMsgQueue();
    printf("msgid:%d\n",msgid);
    //sleep(5);
    //const char* msg="hello bit\n";
    char buf[SIZE];
    while(1)
    {  // recv -->send
        recvMsg(msgid,CLIENT_TYPE,buf);
        printf("client# %s\n",buf);
        printf("please enter# ");
        fflush(stdout);
        ssize_t s=read(0,buf,sizeof(buf)-1);
        if(s>0)
        {
            buf[s-1]='\0';
            sendMsg(msgid,SERVER_TYPE,buf);
        }
        //sleep(1);
    }
    destroyMsgQueue(msgid);
    return 0;
}
client.c:
#include "comm.h"
int main()
{
    int msgid = getMsgQueue();
    printf("msgid:%d\n",msgid);
    char buf[SIZE];
    while(1)
    {  // send --> recv
        printf("please enter# ");
        fflush(stdout);
        ssize_t s=read(0,buf,sizeof(buf)-1);
        if(s>0)
        {
            buf[s-1]='\0';
            sendMsg(msgid,CLIENT_TYPE,buf);
        }
        recvMsg(msgid,SERVER_TYPE,buf);
        printf("server# %s\n",buf);
    }
    return 0;
}
Makefile:
client_=client
server_=server
cc=gcc
cliSrc = client.c comm.c
serSrc = server.c comm.c
.PHONY:all
all:$(client_) $(server_)
$(client_):$(cliSrc)
    $(cc) -o $@ $^
$(server_):$(serSrc)
    $(cc) -o $@ $^
.PHONY:clean
clean:
    rm -f $(client_) $(server_)