INTER-PROCESS COMMUNICATION AND SYNCHRONISATION : Lesson-7: Pipe, socket and RPC

1. INTER-PROCESS COMMUNICATION AND SYNCHRONISATION: Lesson-7: Pipe, socket and RPC Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

2. 1. Pipe 1. Pipe is a device with the functions create, connect and delete and functions similar to a device driver (open, write, read, close) and include. - A message-pipe is an IPC queue of messages between two given inter-connected tasks or two sets of tasks. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

3. Pipe-device Functions Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

4. 2. An OS can handle a pipe IPC as a virtual device when writing and reading from the pipe. The C command are similar to fwrite with a pipe name to write into a named file, and C command fread with name to read from a named pipe. An OS handles stream of bytes into the pipes similar to Java PipedInputOutputStreams. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

5. Task A Pipe Device p Task A sending messages into a pipe and task D receiving that Task D Task C m1 m1 m2 read m1 write m1 read m2 Pipe Device functions create, connect, open, write, read, close, delete write m2 read m3 write m3 Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

6. 3. One task in a set of tasks can write through an OS scheduler to a pipe at the back pointer address, *pBACK. 4. Other task in a set of tasks can read through an OS scheduler from a pipe at the front pointer address, *pFRONT. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

7. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

8. 5. In a pipe, there may be no fixed number of bytes per message with an initial pointer for the back and front and there may be no limiting final back pointers. A pipe can therefore be unlimited and have a variable number of bytes between the initial and final pointers.   Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

9. Pipe Functions Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

10. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

11. 2. Socket 1. Two processes (or sections of a task) at two sets of ports interconnect (perform inter process communication) through a socket at each. [These are virtual (logical), and not physical sockets.] Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

12. 2. A socket is a stream between two specified sections (ports) at the specified sets (addresses) sent with a port-specific protocol. Each socket may have the process address (similar to a network or IP address) and section (similar to a port) specification. The sections (or ports or tasks) and sets of processes (addresses) may be on the same computer or on a network. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

13. Process_i Port_j Socket Device S1 Process i port j socket for the messages that socket at process m port n receives Process_m Port_n Task C Socket Device S2 write S, m1 m1 m1 m2 read S read S read S write S, m2 Device functions of Sockets create, socketS1 (port_j, address_i), socketS2 (port_ n, address_m), open, write, read, close, delete write S, m3 Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

14. 3. There has to be a specific protocol in which the messages at the socket interconnect between (i, j) and (m, n). [i and m are process addresses, and j and n are port or section specifications] A pipe does not have protocol based inter-processor communication, while socket provides that. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

15. 4. A socket can be a client-server socket. Client Socket and server socket functions are different. A socket can be a peer-to-peer socket IPC. At source and destination sockets have similar functions. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

16. 3. Remote Procedure Call (RPC) 1. Provides the inter task communication when a task is at system 1 and another task is at system 2. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

17. 2. Both systems work in the peer-to-peer communication mode. Each system in peer-to-peer mode can make an RPC. • 3. An RPC permits remote invocation of the processes in the distributed systems. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

18. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

19. Summary Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

20. We learnt the following IPC functions at an OS • Pipe, Sockets and Remote procedure calls (RPCs) Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

21. Pipe is a queue or stream of messages that connects the two tasks and the pipe functions are similar to the device functions and IO stream functions. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

22. AnOS provides the sockets for the inter task communication like in a network or client server architecture. Socket has the protocol based IPC functions while pipe functions are simple without the protocol functions. • The RPCs are used for distributed tasks. Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.

23. End of Lesson-7: Pipe, socket and RPC Chapter-8 L7: "Embedded Systems - Architecture, Programming and Design" , Raj Kamal, Publs.: McGraw-Hill, Inc.