메시지큐를이용한 IPC 프로그램구현과제보고서 1. 과제의목적 1 리눅스가지원하는프로세스간통신방식중다수의프로세스사이에구조화된데이터블럭, 즉메시지를전달하는데주로사용되는메시지큐방식에대하여무엇인지, 어떻게사용하는지공부한다. 2 공부한내용을점검하기위해기작성된 epda 프로세스관

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1 [ R E P O R T ] 정보통신공학전공 김성태

2 메시지큐를이용한 IPC 프로그램구현과제보고서 1. 과제의목적 1 리눅스가지원하는프로세스간통신방식중다수의프로세스사이에구조화된데이터블럭, 즉메시지를전달하는데주로사용되는메시지큐방식에대하여무엇인지, 어떻게사용하는지공부한다. 2 공부한내용을점검하기위해기작성된 epda 프로세스관리프로그램과 sms 메시지전송에뮬레이션프로그램을활용하여 sms 전송프로그램을작성하고동작을확인해본다. 1 Linux 2 GCC 2. 필요환경 3. 과제수행내역 1 메시지큐에대한 STUDY 2 epda 프로그램구현 4. 과제수행 1 메시지큐에대한 STUDY 메세지버퍼 (Message buffer) /* message buffer for msgsnd and msgrcv calls */ /* msgsnd 와 msgrcv 호출을위한메세지버퍼 */ struct msgbuf { long mtype; /* type of message 메세지타입 */ char mtext[1]; /* message text 메세지내용 */ ; 커널 msg 구조 (Kernel msg structure) /* 시스템상에서각큐에대한 msqid 구조 */ struct msqid_ds { struct ipc_perm msg_perm; struct msg *msg_first; /* first message on queue 큐의처음메세지 */ struct msg *msg_last; /* last message in queue 큐의마지막메세지 */ time_t msg_stime; /* last msgsnd time 마지막으로 msgsnd 가수행된시간 */ time_t msg_rtime; /* last msgrcv time 마지막으로 msgrcv 가수행된시간 */ time_t msg_ctime; /* last change time 마지막으로 change 가수행된시간 */ struct wait_queue *wwait;

3 ; struct wait_queue *rwait; ushort msg_cbytes; ushort msg_qnum; ushort msg_qbytes; /* max number of bytes on queue 큐의최대바이트수 */ ushort msg_lspid; /* pid of last msgsnd 마지막으로 msgsnd 를수행한 pid*/ ushort msg_lrpid; /* last receive pid 마지막으로받은 pid*/ 커널 ipc perm 구조 (Kernel ipc perm structure) struct ipc_perm { key_t key; ushort uid; /* owner euid and egid */ ushort gid; ushort cuid; /* creator euid and egid */ ushort cgid; ushort mode; /* access modes see mode flags below */ ushort seq; /* slot usage sequence number */ ; 시스템호출 :msgget() (SYSTEM CALL:msgget()) SYSTEM CALL: msgget(); PROTOTYPE: int msgget ( key_t key, int msgflg ); RETURNS: 성공시메세지큐의확인자 (message queue identifier) -1 on error: errno = EACCESS ( 접근권한이없음 ) EEXIST ( 큐가이미존재하여만들수없음 ) EIDRM ( 큐에삭제표시가되어있음 ) ENOENT ( 큐가존재하지않음 ) ENOMEM ( 큐를만들기에메모리가부족함 ) ENOSPC ( 최대큐의갯수를초과함 ) NOTES: 시스템호출 :msgsnd() (SYSTEM CALL:msgsnd()) SYSTEM CALL: msgsnd(); PROTOTYPE: int msgsnd ( int msqid, struct msgbuf *msgp, int msgsz, int msgflg ); RETURNS: 0 on success -1 on error: errno = EAGAIN (queue is full, and IPC_NOWAIT was asserted) EACCES (permission denied, no write permission) EFAULT (msgp address isn't accessable - invalid) EIDRM (The message queue has been removed) EINTR (Received a signal while waiting to write) EINVAL (Invalid message queue identifier, nonpositive message type, or invalid message size) ENOMEM (Not enough memory to copy message

buffer) NOTES: 시스템호출 :msgctl() (SYSTEM CALL:msgctl()) SYSTEM CALL: msgctl(); PROTOTYPE: int msgctl ( int msgqid, int cmd, struct msqid_ds *buf ); RETURNS: 0 on success -1 on error: errno = EACCES (No

4 buffer) NOTES: 시스템호출 :msgctl() (SYSTEM CALL:msgctl()) SYSTEM CALL: msgctl(); PROTOTYPE: int msgctl ( int msgqid, int cmd, struct msqid_ds *buf ); RETURNS: 0 on success -1 on error: errno = EACCES (No read permission and cmd is IPC_STAT) EFAULT (Address pointed to by buf is invalid with IPC_SET and IPC_STAT commands) EIDRM (Queue was removed during retrieval) EINVAL (msgqid invalid, or msgsz less than 0) EPERM (IPC_SET or IPC_RMID command was issued, but calling process does not have write (alter) access to the queue) NOTES:0) 2 epda 구현 사진 1: 전체실행화면

number request message to pbook task smessage.type = SMS; stext.sourcetasknumber = PBOOK; stext.

5 사진 2: SMS task 사진 3: PBOOK task 사진 4: SMS.log file 3 소스파일 PBOOK.c if(rtext->sourcetasknumber == SMS && rtext->code == REQUEST) { // send the recipient's telephone number request message to pbook task smessage.type = SMS; stext.sourcetasknumber = PBOOK; stext.code = RESPONSE; strcpy(stext.recipientname, rtext->recipientname); // strcpy(mbuf, rtext->data); // StructCopy(smessage.text, &stext, BUFSIZ); // pbook task

6 for(i=0;i<max_num;i++) { //initialize phone book with null string strcpy(pbook[i].num, "\0"); strcpy(pbook[i].name, "\0"); strcpy(pbook[max_num-1].num, " "); //insert the tjkim record at the end of the pbook strcpy(pbook[max_num-1].name, "stkim"); //which is to emulate the pbook task if((i = get_phone_number(stext.recipientname)) == -1) { strcpy(stext.recipientnumber, "There is no number!\0"); strcpy(stext.recipientnumber, pbook[i].num); strcpy(stext.data, rtext->data); StructCopy(smessage.text, &stext, BUFSIZ); SMS.c // Send the prepared message if(msgsnd(mqid, (void *)&smessage, BUFSIZ, 0) == -1) { fprintf(stderr, "Fail to send message!!"); exit(1); MessageLog(flog, "TX", smessage); nsmessage++; // if there is no message to recive, return if(msgrcv(mqid, (void *)&rmessage, BUFSIZ, SMS, IPC_NOWAIT) == -1) return; MessageLog(flog, "RX", rmessage); nrmessage++; rtext = (struct SMSTextFormat *) rmessage.text; // if receives the sms sending request from main task, request the number translation service to pbook task

7 if(rtext->sourcetasknumber == MAIN && rtext->code == REQUEST) { // send the recipient's telephone number request message to pbook task smessage.type = PBOOK; stext.sourcetasknumber = SMS; stext.code = REQUEST; strcpy(stext.recipientname, rtext->recipientname); strcpy(mbuf, rtext->data); StructCopy(smessage.text, &stext, BUFSIZ); // Send the prepared message if(msgsnd(mqid, (void *)&smessage, BUFSIZ, 0) == -1) { fprintf(stderr, "Fail to send message!!"); exit(1); MessageLog(flog, "TX", smessage); nsmessage++; if(rtext->sourcetasknumber == PBOOK && rtext->code == RESPONSE) { // emulate the SMS message sending by transmitting it into sms.log file instead of radio channel fprintf(flog, "%s", asctime(&t)); // write calendar time in front of message. fprintf(flog, "Recipient Name = %s: ", rtext->recipientname); fprintf(flog, "Recipient Number = %s: ", rtext->recipientnumber); fprintf(flog, "message = %s\n", mbuf); fflush(flog); 5. 느낀점 그동안알고있던부분을다시공부하는격이었는데... 이번의과제는당시공부를했을때대충한부분이어 서조금힘들었습니다. 하지만그동안잊고있던개념들을다시금생각해보는좋은계기가되었으며, 제자 신의부족한부분을돌이켜보는기회가되었습니다. 6. 본인역할 1 책을참고하여스스로작성하였음.

8 1 없음. 7. 참고사이트

Chap06(Interprocess Communication).PDF

Chap06(Interprocess Communication).PDF Interprocess Communication 2002 2 Hyun-Ju Park Introduction (interprocess communication; IPC) IPC data transfer sharing data event notification resource sharing process control Interprocess Communication