Rensselaer polytechnic institute csci 4210 operating systems david goldschmidt ph d
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Rensselaer Polytechnic Institute CSCI-4210 – Operating Systems David Goldschmidt, Ph.D. Operating Systems {week 10 }. Interprocess communication (IPC). Why is it beneficial for an operating system to enable processes to communicate with one another? Share information Cooperation

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Operating Systems {week 10 }

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Rensselaer polytechnic institute csci 4210 operating systems david goldschmidt ph d

Rensselaer Polytechnic Institute

CSCI-4210 – Operating Systems

David Goldschmidt, Ph.D.

Operating Systems{week 10}


Interprocess communication ipc

Interprocess communication (IPC)

  • Why is it beneficial for an operating systemto enable processes to communicatewith one another?

    • Share information

    • Cooperation

    • Computational speed-up viaparallel programming

    • Modularity of program design

    • Convenience


Ipc mechanisms

IPC mechanisms

  • Message Passing

  • Shared Memory

both IPC mechanisms

require a protocol

and synchronization


Client server communication

Client-server communication

  • Processes may communicate on the same machine or across multiple machines

    • Use sockets for interprocessclient-server communication

    • Use remote procedure calls (RPCs)to call procedures across a network

    • In Java, use remote method invocation (RMI) to call a method on an object in a different virtual machine


Remote procedure calls i

Remote procedure calls (i)


Remote procedure calls ii

Remote procedure calls (ii)

  • Using RPC, heterogeneous operating systems can interact with one another


Marshaling parameters

Marshaling parameters

  • RPCs can be made across a mix ofmachines and operating systems

    • All parameters must be marshaledto ensure proper interpretation

    • Consider date representations

      • YYYY-MM-DD or MM-DD-YYYY or DD-MM-YYYY

    • Also consider big endian versus little endian integer representations

      • (see http://en.wikipedia.org/wiki/Endianness)


Remote method invocation

Remote method invocation

  • RMI is a Java mechanism similar to RPCs

    • RMI enables a running Java program to call a method on a remote object running on a separate Java Virtual Machine

this requires

object serialization


Sockets i

listener socket

128.113.2.9:80

server

socket

128.113.2.9:9500

client

socket

66.195.8.34:8123

Sockets (i)

  • A socket is an endpoint for communication

    • Communication takes place over a pair of sockets

<ip-address>:<port>


Sockets ii

Sockets (ii)

  • Pitfalls of socket-based communication between client and server include:

    • Once a server binds to a port,no other program may listenon that port

    • If client and server do not obeythe rules of the protocol,errors occur


Transmitting objects via sockets

server

client

Transmitting objects via sockets

  • In Java, we transmit primitive data types (e.g. int, double) using DataInputStreamand DataOutputStream

    • To transmit objects, use ObjectInputStreamand ObjectOutputStream instead

this requires

object serialization


Serializing objects i

Serializing objects (i)

  • Objects exist in a JVM’s memory space

    • To transmit an object over a socket,we must first serialize the object

    • For an object to be serializable, its class definition must implement thejava.io.Serializable interface

    • Also useful for saving runtime objects to a file


Serializing objects ii

Serializing objects (ii)

  • The Serializable interface has no methods

    • Simply identifies a class as being serializable

    • And enables the use of readObject() and writeObject() methods of ObjectInputStream and ObjectOutputStream

Student

object

Student

object

network

serialized object

writeObject()

readObject()


Serializing objects iii

Serializing objects (iii)

  • Classes that are not serializable include:

    • java.lang.Thread

    • java.io.OutputStream

    • java.net.Socket

    • etc.

  • Such classes refer to operating system resources, which are not serializable


Serializing objects iv

Serializing objects (iv)

  • Serialized objects are assigned a unique identifier as a means to version control

    • If you write object X to a socket or file,then modify the source code of class X andrecompile the .class file, loading object Xresults in an InvalidClassException runtime exception

    • All processes must be using the same version


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