Linux-interprocess communication-Message Queuing

I. Definition of message queue

Message Queuing can compensate for the lack of pipelines and implement bidirectional interaction data, which is a way for a process to send a process block to another process. Unlike pipelines, pipelines are based on byte streams, Message Queuing is message-based, and Message Queuing reads are not necessarily FIFO.

Second, the creation of message queue

Through the function int messget (key_t key,int MSGFLG);

Key: Port number, can have ftok generation.

MSGFLG:

Ipc_crtat If the IPC does not exist, create an IPC resource,

IPC_EXCL: It is common to use with Ipc_creat to guarantee that the resulting object is new, not open.

Third, read the data to the message queue

MSGRCV messages taken from the queue

ssize_t MSGRCV (int msqid,void *msgp,size_t msgsz,long msgtyp,int msgflg);

MSGSND putting messages in the queue

int msgsnd (int msqid,const void *msgp,size_t msgsz,int MSGFLG);

Iv. Setting Message Queuing properties

int msgctl (int msgqid,int cmd,struct msqid_ds *buf);

You can view functions with the man function name * * *

Program code:

Coom.h

  1  #pragma  once  2  #include <stdio.h>  3  #include < stdlib.h>  4  #include <string.h>  5  #include <sys/types.h>   6  #include <sys/ipc.h>  7  #include <sys/msg.h>    8   #define  _PATH_  "."   9  #define  _PROCID_ 0x776 10  #define  _size 1024 11 # define serve_msgtype 1 12  #define  cliect_msgtype 2  13 typedef  struct message 14 { 15   long mtype; 16    Char mtext[_size]; 17 }message; 18 int create_msg (int msg_num);  19  int drstroy_msg (int msg_id);  20 int set_msg ();  21 int get_msg ();  22 int msg_send (Int msg_id,const char* msg,long type); 23 Int msg_rec (Int msg_id ,char buf[],long type); 

Comm. C

  1  #include "comm.h"   2  int create_msg (int msg_num)   3  {  4   key_t _key=ftok (_path_,_procid_);   5   if ( _key < 0)   6   {  7     perror ("Ftok" );  8     return -1;  9   } 10    int ret= msgget (_key,msg_num);  11    if (ret < 0)  12    { 13     perror ("Msgget"); 14      return -1; 15    } 16  return ret; 17  } 18 int drstroy_msg (int msg_id)  19 { 20   if (Msgctl ( Msg_id,ipc_rmid,null)  < 0)  21   { 22     perror ("Msgctl");  23     return -1; 24   }else{ 25      printf ("remove message_queue\n"); 26     return 0; 27    } 28 } 29 int set_msg ()  30 { 31   umask (0);  32   return create_msg (ipc_creat | ipc_excl |0666);  33 } 34 int get_msg ()  35 { 36      return create_msg (ipc_creat);  37 } 38 int msg_send (int msg_id, Const char* msg,long type)  39 { 40   struct message _ msg; 41   _msg.mtype=type; 42   strcpy (_msg.mtext,msg); 43    if (Msgsnd (Msg_id,&_msg,strlen (_msg.mtext), 0) < 0)  44   { 45      perror ("Msg_send error"); &nbsP;46     return -1; 47   } 48   return  0; 49 } 50 int msg_rec (Int msg_id,char buf[],long type)  51  { 52   struct message _msg; 53   memset (_msg.mtext, ' ', _size);  54   if (MSGRCV (msg_id,&_msg,_size,type,0) < 0)  55    { 56     perror ("Msg_receve error"); 57      return -1; 58   } 59   strcpy (buf,_msg.mtext);  60    return 0; 61 } 62

Client.c

  1  #include "comm.h"   2 int main ()   3 {  4   int msg_id=get_msg ();   5  if (msg_id<0)   6  {   7   perror ("error");   8   exit (1);   9  } 10    char buf[_size]; 11  while (1)  12  { 13    fflush (stdout);  14   printf ("please client input: "); 15    memset (buf, ' _size '); 16   fgets  (buf,sizeof (BUF), stdin); 17    if (Msg_send (msg_id,buf,cliect_msgtype) < 0)  18     { 19        perror ("Send fail"); 20        exit (1);  21     } 22  23   if (Msg_rec ( Msg_id,buf,serve_msgtype) <0)  24     { 25       perror ("Recve  fail ");  26       exit (1);  27     }  28   printf ("serve:%s"  ,buf);  29  } 30   return  0; 31 }

Server.c

  1  #include   "comm.h"   2 int main ()   3 {  4    int msg_id=set_msg ();   5   if (msg_id<0)   6    {  7     perror ("mig_id");  8      exit (1);   9   } 10   printf ("%d\n", msg_id); 11    char buf[_size]; 12   while (1)  13   { 14       if (Msg_rec (msg_id,buf,cliect_msgtype) < 0)  15      { 16       perror ("Recve fail"); 17        exit (1); 18     } 19      else 20     { 21       printf (" Client :%s ", buf);   22     } 23     printf ("Server please input:    24     fflush (stdout);  25     memset (buf , ' _size ',  26     fgets (Buf,_size,stdin); 27      if (Msg_send (msg_id,buf,serve_msgtype) <0)  28     { 29        perror ("Send fail");  30       exit ( 1);  31     } 32   } 33   drstroy_msg (msg _ID);  34   return 0; 35 }

Operation Result:

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Linux-interprocess communication-Message Queuing