进程间通信-消息队列

互斥：矛盾 

同步：协作

消息队列

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/msg.h>

• int msgget(key_t key,int msgflg);
• int msgctl(int msgid,int cmd,stuct msqid_ds *buf);
• cmd:
• 　　IPC_RMID
• 　　IPC_STAT
• 　　IPC_SET

• int msgend(int msqid,const void *msgp,sie_t msgsz,int msgflg);
  • msgflg:
    • IPC_NOWAT表示队列蛮不等待，返回EAGAIN
• ssize_t msgrcv(int msqid,void *msgp, size_t msgsz,long msgtyp,int msgflg);
• 基于消息队列的客户端

  •  1 #include <unistd.h>
     2 #include <sys/types.h>
     3 #include <sys/ipc.h>
     4 #include <sys/msg.h>
     5 #include <stdlib.h>
     6 #include <stdio.h>
     7 #include <errno.h>
     8 #include <string.h>
     9 
    10 #define ERR_EXIT(m)\
    11     do\
    12     {\
    13         perror(m);\
    14         exit(EXIT_FAILURE);\
    15     }while(0)
    16 
    17 #define MSGMAX 8192
    18 
    19 struct msgbuf
    20 {
    21     long mtype;
    22     char mtext[MSGMAX];
    23 };
    24 
    25 void echo_cli(int msgid)
    26 {
    27     int n;
    28     int pid;
    29     pid = getpid();    
    30     struct msgbuf msg;
    31     memset(&msg,0,sizeof(msg));
    32     *((int*)msg.mtext) = pid;
    33     msg.mtype = 1;
    34     while(fgets(msg.mtext+4,MSGMAX, stdin) != NULL)
    35     {
    36         msg.mtype = 1;
    37         if(msgsnd(msgid,&msg,4+strlen(msg.mtext+4), 0) < 0)
    38             ERR_EXIT("msgsnd");
    39 
    40         memset(msg.mtext+4, 0, MSGMAX-4);
    41         if((n = msgrcv(msgid, &msg, MSGMAX, pid, 0)) < 0)
    42             ERR_EXIT("msgrcv");
    43 
    44         fputs(msg.mtext+4,stdout);
    45         memset(msg.mtext+4, 0, MSGMAX-4);
    46     }
    47 }
    48 
    49 int main(int argc,char* argv[])
    50 {
    51     int msgid;
    52     msgid = msgget(1234,0);
    53     if(msgid == -1)
    54         ERR_EXIT("msgget failed\n");
    55     printf("msgget ok,msgid=%d\n",msgid);
    56     echo_cli(msgid);
    57 }

• 基于消息队列的服务器

  •  1 #include <unistd.h>
     2 #include <sys/types.h>
     3 #include <sys/ipc.h>
     4 #include <sys/msg.h>
     5 #include <stdlib.h>
     6 #include <stdio.h>
     7 #include <errno.h>
     8 #include <string.h>
     9 
    10 #define ERR_EXIT(m)\
    11     do\
    12     {\
    13         perror(m);\
    14         exit(EXIT_FAILURE);\
    15     }while(0)\
    16 
    17 #define MSGMAX 8192
    18 struct msgbuf
    19 {
    20     long mtype;
    21     char mtext[MSGMAX];
    22 };
    23 
    24 void echo_srv(int msgid)
    25 {
    26     int n;
    27     struct msgbuf msg;
    28     memset(&msg, 0, sizeof(msg));
    29     while(1)
    30     {
    31         if((n = msgrcv(msgid,&msg,MSGMAX,1,0)) < 0)
    32             ERR_EXIT("msgsnd");
    33         int pid;
    34         pid = *((int*)msg.mtext);
    35         
    36         fputs(msg.mtext+4,stdout);
    37         msg.mtype = pid;
    38         msgsnd(msgid, &msg, n, 0);
    39     }
    40 }
    41 
    42 int main(int argc,char* argv[])
    43 {
    44     int msgid;
    45     msgid = msgget(1234,IPC_CREAT | 0666);
    46     if(msgid == -1)
    47         ERR_EXIT("msgget failed\n");
    48     printf("msgget ok,msgid=%d\n",msgid);
    49 
    50     echo_srv(msgid);
    51 }