IPC in UNIX
Inter-Process Communication : Mechanism for various processes to communicate among them.
다양한 프로세스가 프로세스 간에 통신하기 위한 메커니즘
- Different processes run on different address space.
각기 다른 프로세스가 각기 다른 주소 공간에서 실행
- OS needs to provide mechanisms to communicate -> IPC.
OS는 통신하기 위한 메커니즘을 제공 -> IPC.
Types of IPCs in UNIX
- Traditional UNIX IPCs : signal, pipe, socket
- System V IPCs : message queue, semaphore, shared memory
Pipe
Unidirectional byte streams which connect one process into the other process.
한 프로세스를 다른 프로세스에 연결하는 단방향 바이트 스트림
- The data written at one end of the channel is read at the other end.
채널의 한 쪽 끝에서 기록된 데이터를 다른 쪽 끝에서 읽습니다.
- From a logical point of view, a pipe can be compared to a FIFO queue of characters.
논리적인 관점에서 파이프는 문자의 FIFO 큐와 비교될 수도
-
No structured communication
It is not possible to know the size, sender/receiver of data contained in the pipe.
구조화된 통신 없음 : 파이프에 포함된 데이터의 크기, 송신자/수신자를 알 수 없음 -
Access to pipes is achieved by reading / writing from/to file descriptors.
Pipe Used by Commands
One current usage of the pipe mechanism is performed by means of the command line interpreter when commands are linked:
파이프 메커니즘의 현재 사용 중 하나는 명령이 연결된 경우 명령줄 인터프리터를 통해 수행됩니다.
(e.g., > ps -aux | grep root | tail)
Ordinary (Anonymous) Pipe
Created by a process and the transmission for associated descriptors is achieved only by inheritance by its descendants (parent <-> child).
프로세스에 의해 생성되고 관련 설명자에 대한 전송은 하위 항목에 의한 상속에 의해서만 수행됨
(i.e., by creating a child process using fork() system call)
Restrictive in that it only allows communication between processes with a common ancestor which is a creator of a pipe.
파이프의 작성자인 공통 조상을 가진 프로세스 간의 통신만 허용한다는 점에서 제한적
Use of Pipe Example
fd[0] : read
fd[1] : write
"Hello World"
Named Pipe (FIFO)
Remove the constraint of anonymous pipe (i.e., no name, only used between processes that have a parent process in common) because they are entries in the file system.
익명 파이프는 파일 시스템의 항목이기 때문에 해당 제약 조건을 제거
Has a name and handled exactly like files with respect to file operations (e.g., open, close, read, write).
Created by mkfifo or mknod commands.
Can be created by C functions : mkfifo().
- int mkfifo(const char *path, mode_t mode);
Reading from / writing to a named pipe can be achieved by using standard read() and write() system calls.
Communication in Client-Server Systems
- Sockets
- Remote Procedure Calls
Sockets
A socket is defined as an endpoint for communication.
소켓은 통신을 위한 끝점으로 정의
Concatenation of IP address and port number
IP 주소와 포트 번호의 연결
The socket 161.25.19.8:1625 refers to port 1625 on host 161.25.19.8
Communication consists between a pair of sockets.
Socket Communication
Remote Procedure Calls
Remote procedure call (RPC) abstracts procedure calls between processes on networked systems.
Main Components of RPC
