Multithreaded Server

This example of a multithreaded server process has a main thread that loops continuously, creating a pipe instance and waiting for a client process to connect. When a client process connects, the server process creates a thread to service that client and the loop starts over. It is possible for a client process to connect successfully to the pipe instance in the interval between calls to the CreateNamedPipe and ConnectNamedPipe functions. If this happens, ConnectNamedPipe returns FALSE, and GetLastError returns ERROR_PIPE_CONNECTED.

The thread created to service each pipe instance reads requests from the pipe and writes replies to the pipe until the client process closes its handle. When this happens, the thread flushes the pipe, disconnects, closes its pipe handle, and terminates.

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <windows.h>

VOID InstanceThread(LPVOID);

VOID GetAnswerToRequest(LPTSTR, LPTSTR, LPDWORD);

int xx = 0;

DWORD main(VOID)

{

BOOL fConnected;

DWORD dwThreadId;

HANDLE hPipe, hThread;

LPTSTR lpszPipename = "\\\\.\\pipe\\mynamedpipe";

// The main loop creates an instance of the named pipe and

// then waits for a client to connect to it. When the client

// connects, a thread is created to handle communications

// with that client, and the loop is repeated.

for (;;)

{

hPipe = CreateNamedPipe(

lpszPipename, // pipe name

PIPE_ACCESS_DUPLEX, // read/write access

PIPE_TYPE_MESSAGE | // message type pipe

PIPE_READMODE_MESSAGE | // message-read mode

PIPE_WAIT, // blocking mode

PIPE_UNLIMITED_INSTANCES, // max. instances

BUFSIZE, // output buffer size

BUFSIZE, // input buffer size

PIPE_TIMEOUT, // client time-out

NULL); // no security attribute

if (hPipe == INVALID_HANDLE_VALUE)

MyErrExit("CreatePipe");

// Wait for the client to connect; if it succeeds,

// the function returns TRUE. If the function returns FALSE,

// GetLastError returns ERROR_PIPE_CONNECTED.

fConnected = ConnectNamedPipe(hPipe, NULL) ?

TRUE :

(GetLastError() == ERROR_PIPE_CONNECTED);

if (fConnected)

{

// Create a thread for this client.

hThread = CreateThread(

NULL, // No security attribute

0, // Default stack size

(LPTHREAD_START_ROUTINE) InstanceThread,

(LPVOID) hPipe, // Thread parameter

0, // Not suspended

&dwThreadId); // Returns thread ID

if (hThread == INVALID_HANDLE_VALUE)

MyErrExit("CreateThread");

}

else

// The client could not connect, so close the pipe.

CloseHandle(hPipe);

}

return 1;

}

VOID InstanceThread(LPVOID lpvParam)

{

CHAR chRequest[BUFSIZE];

CHAR chReply[BUFSIZE];

DWORD cbBytesRead, cbReplyBytes, cbWritten;

BOOL fSuccess;

HANDLE hPipe;

// The thread's parameter is a handle to a pipe instance.

hPipe = (HANDLE) lpvParam;

while (1)

{

// Read client requests from the pipe.

fSuccess = ReadFile(

hPipe, // handle to pipe

chRequest, // buffer to receive data

BUFSIZE, // size of buffer

&cbBytesRead, // number of bytes read

NULL); // not overlapped I/O

if (! fSuccess || cbBytesRead == 0)

break;

GetAnswerToRequest(chRequest, chReply, &cbReplyBytes);

// Write the reply to the pipe.

fSuccess = WriteFile(

hPipe, // handle to pipe

chReply, // buffer to write from

cbReplyBytes, // number of bytes to write

&cbWritten, // number of bytes written

NULL); // not overlapped I/O

if (! fSuccess || cbReplyBytes != cbWritten) break;

}

// Flush the pipe to allow the client to read the pipe's contents

// before disconnecting. Then disconnect the pipe, and close the

// handle to this pipe instance.

FlushFileBuffers(hPipe);

DisconnectNamedPipe(hPipe);

CloseHandle(hPipe);

}

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