interprocee communication

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Interprocess CommunicationInterprocess Communication

2007/06/06


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Agenda Agenday Introductiony A nonymous pipesy

Named pipesy Mailslots

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IntroductionIntroductiony Perform directly process-to-process

communicationy Relative A PI:

Readfile() and Writefile()

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A nonymous pipes A nonymous pipes

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Exercise 1Exercise 1y Please refer to Fi gure 11-1 and

Pro gram 11-1, and them finish them.Pro gram 11-1 create pipe and you stillneed to create Pro gram 1 and Pro gram2

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Named pipesNamed pipes

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Win32 A PI Win32 A PI

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Server:

H A NDLE Create N amedPipe (LPCTSTR lpPipeName,DWORD dwOpenMode,DWORD dwPipeMode,

DWORD nMaxInstance,DWORD cbOutBuf,DWORD cdInBuf,DWORD dwTimeout,LPSECURITY_ A TTRIBUT ES lpsa,

);

BOOL Connect N amedPipe (H A NDLE hNamedPipe,LPOV ERL A PP ED lpOverlapped,

);

BOOL Disconnect N amedPipe (H A NDLE hNamedPipe,

);

Client:

BOOL Wait N amedPipe (LPCTSTR lpPipeName,DWORD dwTimeout,

);

The format for pipe name\\ .\ pipe \[ path]pipename\\ servername \ pipe \[ path]pipe

name


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A dvanced function A dvanced functiony To instead of WriteFile() and

ReadFiled()T ransact N amedPipe()x

First convenientx Create permanent connect that causelimited number of clients

Call N amedPipe()x Second convenientx Create temporary connectionx Is uses to specify the pipe, and set a

time-out period

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Combine :CreateFile() WriteFile()

ReadFile()CloaseHandle()


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Compare anonymous pipe andCompare anonymous pipe andnamed pipenamed pipe

Duplex half-duplex full-duplex

Data unit Character-based Character-based/messa ge based

IndependentInstance No Yes

Location One the samecomputer

On the samecomputer or different

computers

Set security Yes Yes13


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Exercise 2Exercise 2y Please refer to pro gram 11-2, and write

a simple named pipe that can support10 client to connect.

Usin g CallNamedPipe()

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CharacteristicsCharacteristicsy Broadcast mechanismy One-directionaly Can have multiple writers and readers, but often

is one-to-many y Can be located over a network domainy Client writes and server readsy Only one specific mailslot name can exist on the

same machine

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How to useHow to use mailslotsmailslots

y Server(Reader)Creates a mailslot handle withCreateMail S lot() .

Then waits to receive a mailslotmessa ge with a R eadFile() call

y Client(Writer)A w rite-only client open the

mailslot with CreateFile() Write messa ges with WriteFile()

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Server (CreateMailslot) \\.\mailslot\

Client(CreateFile)\\*\ mailslot \ mailslotname\\< computername> \ mailslot \ mailslot name\\< domainname> \ mailslot \ mailslotname\\.\ mailslot \ mailslotname


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Compare named pipes andCompare named pipes and mailslotsmailslots

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N amed pipe Mailslots

Client Server Client Server

NamedPipeHandle orConnection

CreateFileCallNamedPipe,TransactNamedPipe

CreateNamedPipe CreateFile CreateMailslot

A ction Read/write Read/write Write Read

NoteConnection oriented Can broadcast


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Exercise 3Exercise 3y Try to create a mailslot between two

computers, and remember to useGetMailslotInfo () to check themailslot status.

y If you create a mailslot name that is AAA , but these already exists thesame name on the same computer. What is the error code if you use

GetLast Error() to retrieve it .

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