interprocess communication: Message Queuing implements two-way communication

Message Queuing: The operating system provides a buffer that provides a way to send a block of data from one process to another. Message Queuing differs from a pipeline in that Message Queuing is message-based and the pipeline is byte-stream based.

View System Message Queuing command: IPCS-Q

Delete Message Queue command: Ipcrm-q message ID number

Related functions:

Prototype: Generate Message queue:int msgget (key_t key, int msgflg);

Send message: int msgsnd (int msqid, const void *MSGP, size_t msgsz, int msgflg);

Receive message: ssize_t MSGRCV (int msqid, void *msgp, size_t msgsz, Long msgtyp,int MSGFLG);

Set Message Queuing Properties prototype:int msgctl (int msgqid, int cmd, struct msqid_ds *buf);

Parameters: The system defines 3 cmd operations : Ipc_stat, Ipc_set, Ipc_rmid

Ipc_stat:This command is used to obtain a message queue corresponding to theMsqid_dsData structure and save it to the address space defined by BUF.
Ipc_set: This command sets the properties of the message queue, and the properties to be set are stored in buf .
ipc_rmid: removes the msqid identity message queue from the kernel.

  //comm.h  1  #pragma  once  2  #include <stdio.h>   3  #include <stdlib.h>  4  #include <string.h>  5  #include <sys/ types.h>  6  #include <unistd.h>  7  #include <sys/ipc.h>   8  #include <sys/msg.h>  9  #define  _PATH_  "."  10  #define  _PROJ_ID_ 0x777 11  #define  _BLOCK_SIZE_ 1024 12  #define  _SERVER_MSG_TYPE_ 1 13  #define  _client_msg_type_ 2 14 struct  msgbuf 15 { 16     long mtype; 17      char mtext[_block_size_]; 18 }; 19 static int comm_msg_queue ( Int flag);  20 int set_msg_queue ();  21 int get_msg_queue ();  22 int  msg_queue_send (int msg_id,const cHar* msg,long type);  23 int msg_queue_recv (int msg_id,char* msg,long  Type); //comm.c  1  #include "comm.h"   2 static int comm_msg_queue ( Int flag)   3 {  4   5     key_t _ Key=ftok (_path_,_proj_id_);   6     if (_key<0)   7      {  8         perror ("Ftok");   9         return -1; 10      }    11     int msg_id=msgget (_key,flag);  12      if (msg_id<0)  13     { 14          perror ("Msgget"); 15          return -1; 16     }    17     return msg_id;  18 }    19 int set_msg_queue ()  20 { 21      umask (0);  22     return comm_msg_queue (IPC_CREAT| ipc_excl|0666);  23 }    24 int get_msg_queue ()  25 { 26      return comm_msg_queue (ipc_creat);  27 }    28  int msg_queue_send (Int msg_id,const char* message,long type)  29 {  30     struct msgbuf msg; 31      msg.mtype=type; 32     strcpy (msg.mtext,message); 33      if (Msgsnd (Msg_id,&msg,strlen (Msg.mtext), 0) <0)  34     {  35      &nbSp;  perror ("msgsnd"); 36         return -1;  37     }    38     return 0;  //server.c  1  #include "comm.h"   2 int main ()   3 {   4     int msgid=set_msg_queue ();  5      if (msgid<0)   6     {  7          exit (1);  8     }  9      char buf[_block_size_]; 10     printf ("Input quit  endding. \ n ");  11     while (1)  12     { 13          if (MSG_QUEUE_RECV (msgid,buf,_client_msg_type_) <0)  14          { 15              printf ("recv fail\n"); 16              exit (1); 17         } 18          else 19         {  20             if (strcmp ("Quit", buf) ==0 )  21                  return 0; 22              printf ("client:%s\n", buf); 23         } 24          printf ("Input:"); 25          fflush (stdout); &nbsP;26         memset (buf, ' _block_size_ '); 27          gets (BUF); 28          if (Msg_queue_send (msgid,buf,_server_msg_type_) <0)  29          { 30             printf (" Send fail\n ");  31             exit ( 1);  32         } 33     }  34     destroy (MsgId); 35     return 0;  36 } //client.c  1  #include "comm.h"   2 int main ()    3 {  4     int msgid=get_msg_queue ();  5      if (msgid<0)   6     {  7          exit (1);   8     }  9     char  buf[_block_size_]; 10     while (1)  11     {  12         fflush (stdout); 13          printf ("Please input:"); 14          memset (buf, ' n ', _block_size_);  15         gets ( BUF);  16         if (Msg_queue_send (msgid,buf,_CLIENT_MSG_ TYPE_) <0)  17         { 18              printf ("send fail\n"); 19         &Nbsp;    exit (1);  20         } 21          if (MSG_QUEUE_RECV (msgid,buf,_server_msg_type_) <0)  22         { 23              printf ("recv fail\n"); 24              exit (1); 25          } 26         printf ("server:%s\n", buf);  27      } 28     return 0; 29 } // Makefile writing   1 . Phony:all  2 all:server client  3 server:server.c comm.c  4      gcc -o [email protected] $^  5 client: Client.c comm.c  6     gcc -o [email protected] $^   7 . phony:clean  8 clean:  9     rm -f server  Client

Operation Result:

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interprocess communication: Message Queuing implements two-way communication