Message Queuing for inter-process communication between Linux

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One, Message Queuing

1, Concept: "Message Queuing" is a container for saving messages during the transmission of a message

2, Message Queuing is a linked list of messages. You can think of a message as a record, with a specific format and a specific priority.

a process that has write permission to a message queue can add new messages to a message queue in accordance with certain rules;

a process that has read access to a message queue can read messages from the message queue.

Message Queuing is persistent with the kernel.

3, Programming Considerations: When using the data encapsulated into a message, the message into the queue

Programming steps: The use of specific functions can be viewed with the man manual (strongly recommended)

(1) Ftok () Production key

(2) Create/Get Message queue using Msgget (), return value is queue identifier

(3) Send a message using MSGSND ()

Using MSGRCV () to receive messages

(4) Delete Message Queuing using Msgctl ()

4, Example:

SENDMSG.C used to send messages.

//sendmsg.c#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<sys/types.h>#include<sys/ipc.h>#include<sys/msg.h>#include<string.h>structmy_msg{intMtype;//Message Type    Charbuf[ the];} MSG1, MSG2;intMain () {key_t key= Ftok ("./", the); intMsgId = Msgget (Key,0666|ipc_creat); if(-1==MsgId) {Perror ("Msgget failed!!!"); Exit (1); } Msg1.mtype=2; strcpy (Msg1.buf,"Hello, msg2."); Msgsnd (MsgId,&AMP;MSG1,sizeof(MSG1),0);//Blocking//msgsnd (MsgId, &MSG1, sizeof (MSG1), ipc_nowait);//non-blockingMsg2.mtype=1; strcpy (Msg2.buf,"Hello, msg1."); Msgsnd (MsgId,&AMP;MSG2,sizeof(MSG2),0);//Blockingprintf ("message Send complete, press ENTER to destroy message queue \ n");    GetChar (); if(-1==Shmctl (MsgId, Ipc_rmid, NULL)) {Perror ("Shmctl failed"); Exit (2); }    return 0;}

RECVMSG.C used to receive messages.

//recvmsg.c#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<sys/types.h>#include<sys/ipc.h>#include<sys/msg.h>#include<string.h>structmy_msg{intMtype;//Message Type    Charbuf[ the];} msg;intMain () {key_t key= Ftok ("./", the); //Get Message Queuing    intMsgId = Msgget (Key,0); if(-1==MsgId) {Perror ("Msgget failed!!!"); Exit (1); }    intres = MSGRCV (MsgId, &msg,sizeof(msg),2,//a message with a message type of 2 is taken            0); printf ("type:%d, content:%s\n", Msg.mtype, msg.buf); printf ("Message Reception complete, press ENTER to destroy Message Queuing \ n");    GetChar (); if(-1==Shmctl (MsgId, Ipc_rmid, NULL)) {Perror ("Shmctl failed"); Exit (2); }    return 0;}

5, running results

6, get the code

git clone https://github.com/xcywt/xcyipc.git

Some people see this trouble again in the picture of the Bantu try this library is not built. The main lesson is to learn some of the uses of GitHub.

Message Queuing for inter-process communication between Linux