M. Saqib

C++ Client and Server, Overlapped Server and Thread Server

This C++ Program demonstrate the use of pipes to pass a continuous stream of data between processes. It has four parts i.e.

Simple named pipe client that demonstrates the API calls needed to successfully develop a basic named pipe client application.

Overlapped Server demonstrates how to develop an advanced named pipe server that is capable of servicing 5 named pipe instances.

Simple named pipe server that demonstrates the API calls needed to successfully develop a basic named pipe server application.

Advanced named pipe server that is capable of servicing 5 named pipe instances.

Table of Contents

Client Application – Named Client Pipe

Filename: Overlap.cpp

This C++ program is a simple named pipe client that demonstrates the API calls needed to successfully develop a basic named pipe client application. When this application successfully connects to a named pipe, the message “This is a test” is written to the server.

There are four basic steps needed to implement a client:

  1. Wait for a Named Pipe instance to become available using the WaitNamedPipe() API function.
  2. Connect to the Named Pipe using the CreateFile() API function.
  3. Send data to or receive data from the server using the WriteFile() and ReadFile() API functions.
  4. Close the Named Pipe session using the CloseHandle() API functions.

Compile

cl -o Client Client.cpp

Command Line Options:

None

Source Code:

#include <windows.h>
#include <stdio.h>

#define PIPE_NAME "\\\\.\\Pipe\\Jim"

void main(void) {

  HANDLE PipeHandle;
  DWORD BytesWritten;

  if (WaitNamedPipe(PIPE_NAME, NMPWAIT_WAIT_FOREVER) == 0) {
    printf("WaitNamedPipe failed with error %d\n",
      GetLastError());
    return;
  }

  // Create the named pipe file handle
  if ((PipeHandle = CreateFile(PIPE_NAME,
      GENERIC_READ | GENERIC_WRITE, 0,
      (LPSECURITY_ATTRIBUTES) NULL, OPEN_EXISTING,
      FILE_ATTRIBUTE_NORMAL,
      (HANDLE) NULL)) == INVALID_HANDLE_VALUE) {
    printf("CreateFile failed with error %d\n", GetLastError());
    return;
  }

  if (WriteFile(PipeHandle, "This is a test", 14, & BytesWritten,
      NULL) == 0) {
    printf("WriteFile failed with error %d\n", GetLastError());
    CloseHandle(PipeHandle);
    return;
  }

  printf("Wrote %d bytes", BytesWritten);

  CloseHandle(PipeHandle);
}

Overlapped Server – Advanced Named Pipe Server

Filename: Overlap.cpp

This sample demonstrates how to develop an advanced named pipe server that is capable of servicing 5 named pipe instances. The application is an echo server where data is received from a client and echoed back to the client. All the pipe instances are serviced in the main application thread using Win32 overlapped I/O.

Compile:

cl -o overlap overlap.cpp

Command Line Options:

None

Source Code:

#include <windows.h>
#include <stdio.h>
 
#define NUM_PIPES 5
#define BUFFER_SIZE 256

void main(void) {
  HANDLE PipeHandles[NUM_PIPES];
  DWORD BytesTransferred;
  CHAR Buffer[NUM_PIPES][BUFFER_SIZE];
  INT i;
  OVERLAPPED Ovlap[NUM_PIPES];
  HANDLE Event[NUM_PIPES];

  // For each pipe handle instance, the code must maintain the
  // pipes' current state, which determines if a ReadFile or
  // WriteFile is posted on the named pipe. This is done using
  // the DataRead variable array. By knowing each pipe's
  // current state, the code can determine what the next I/O
  // operation should be.
  BOOL DataRead[NUM_PIPES];

  DWORD Ret;
  DWORD Pipe;

  for (i = 0; i < NUM_PIPES; i++) {
    // Create a named pipe instance
    if ((PipeHandles[i] = CreateNamedPipe("\\\\.\\PIPE\\jim",
        PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
        PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, NUM_PIPES,
        0, 0, 1000, NULL)) == INVALID_HANDLE_VALUE) {
      printf("CreateNamedPipe for pipe %d failed "
        "with error %d\n", i, GetLastError());
      return;
    }

    // Create an event handle for each pipe instance. This
    // will be used to monitor overlapped I/O activity on
    // each pipe.
    if ((Event[i] = CreateEvent(NULL, TRUE, FALSE, NULL)) ==
      NULL) {
      printf("CreateEvent for pipe %d failed with error %d\n",
        i, GetLastError());
      continue;
    }

    // Maintain a state flag for each pipe to determine when data
    // is to be read from or written to the pipe
    DataRead[i] = FALSE;

    ZeroMemory( & Ovlap[i], sizeof(OVERLAPPED));
    Ovlap[i].hEvent = Event[i];

    // Listen for client connections using ConnectNamedPipe()
    if (ConnectNamedPipe(PipeHandles[i], & Ovlap[i]) == 0) {
      if (GetLastError() != ERROR_IO_PENDING) {
        printf("ConnectNamedPipe for pipe %d failed with",
          " error %d\n", i, GetLastError());
        CloseHandle(PipeHandles[i]);
        return;
      }
    }
  }

  printf("Server is now running\n");

  // Read and echo data back to Named Pipe clients forever
  while (1) {
    if ((Ret = WaitForMultipleObjects(NUM_PIPES, Event,
        FALSE, INFINITE)) == WAIT_FAILED) {
      printf("WaitForMultipleObjects failed with error %d\n",
        GetLastError());
      return;
    }

    Pipe = Ret - WAIT_OBJECT_0;

    ResetEvent(Event[Pipe]);

    // Check overlapped results, and if they fail, reestablish
    // communication for a new client; otherwise, process read
    // and write operations with the client

    if (GetOverlappedResult(PipeHandles[Pipe], & Ovlap[Pipe], &
        BytesTransferred, TRUE) == 0) {
      printf("GetOverlapped result failed %d start over\n",
        GetLastError());

      if (DisconnectNamedPipe(PipeHandles[Pipe]) == 0) {
        printf("DisconnectNamedPipe failed with error %d\n",
          GetLastError());
        return;
      }

      if (ConnectNamedPipe(PipeHandles[Pipe], &
          Ovlap[Pipe]) == 0) {
        if (GetLastError() != ERROR_IO_PENDING) {
          // Severe error on pipe. Close this
          // handle forever.
          printf("ConnectNamedPipe for pipe %d failed with"
            "error %d\n", i, GetLastError());
          CloseHandle(PipeHandles[Pipe]);
        }
      }

      DataRead[Pipe] = FALSE;
    } else {
      // Check the state of the pipe. If DataRead equals
      // FALSE, post a read on the pipe for incoming data.
      // If DataRead equals TRUE, then prepare to echo data
      // back to the client.

      if (DataRead[Pipe] == FALSE) {
        // Prepare to read data from a client by posting a
        // ReadFile operation

        ZeroMemory( & Ovlap[Pipe], sizeof(OVERLAPPED));
        Ovlap[Pipe].hEvent = Event[Pipe];

        if (ReadFile(PipeHandles[Pipe], Buffer[Pipe],
            BUFFER_SIZE, NULL, & Ovlap[Pipe]) == 0) {
          if (GetLastError() != ERROR_IO_PENDING) {
            printf("ReadFile failed with error %d\n",
              GetLastError());
          }
        }

        DataRead[Pipe] = TRUE;
      } else {
        // Write received data back to the client by
        // posting a WriteFile operation.
        printf("Received %d bytes, echo bytes back\n",
          BytesTransferred);

        ZeroMemory( & Ovlap[Pipe], sizeof(OVERLAPPED));
        Ovlap[Pipe].hEvent = Event[Pipe];

        if (WriteFile(PipeHandles[Pipe], Buffer[Pipe],
            BytesTransferred, NULL, & Ovlap[Pipe]) == 0) {
          if (GetLastError() != ERROR_IO_PENDING) {
            printf("WriteFile failed with error %d\n",
              GetLastError());
          }
        }

        DataRead[Pipe] = FALSE;
      }
    }
  }
}

Simple Named Pipe Server

Filename: Server.cpp

This program is a simple named pipe server that demonstrates the API calls needed to successfully develop a basic named pipe server application. When this application receives a client connection, it reads the data from the pipe and reports the received message.

You need five basic steps to write a named pipe server:

  1. Create a named pipe instance handle using the CreateNamedPipe() API function.
  2. Listen for a client connection on a pipe instance using the ConnectNamedPipe() API function.
  3. Receive from and send data to the client using the ReadFile() and WriteFile() API functions.
  4. Close down the named pipe connection using the DisconnectNamedPipe() API function.
  5. Close the named pipe instance handle using the CloseHandle() API function.

Compile:

cl -o Server Server.cpp

Command Line Options:

None

Source Code:

#include <windows.h>
#include <stdio.h>

void main(void) {
  HANDLE PipeHandle;
  DWORD BytesRead;
  CHAR buffer[256];

  if ((PipeHandle = CreateNamedPipe("\\\\.\\Pipe\\Jim",
      PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, 1,
      0, 0, 1000, NULL)) == INVALID_HANDLE_VALUE) {
    printf("CreateNamedPipe failed with error %d\n",
      GetLastError());
    return;
  }

  printf("Server is now running\n");

  if (ConnectNamedPipe(PipeHandle, NULL) == 0) {
    printf("ConnectNamedPipe failed with error %d\n",
      GetLastError());
    CloseHandle(PipeHandle);
    return;
  }

  if (ReadFile(PipeHandle, buffer, sizeof(buffer), &
      BytesRead, NULL) <= 0) {
    printf("ReadFile failed with error %d\n", GetLastError());
    CloseHandle(PipeHandle);
    return;
  }

  printf("%.*s\n", BytesRead, buffer);

  if (DisconnectNamedPipe(PipeHandle) == 0) {
    printf("DisconnectNamedPipe failed with error %d\n",
      GetLastError());
    return;
  }

  CloseHandle(PipeHandle);
}

Thread Server – Advanced Named Pipe Server

Filename: Threads.cpp

This sample demonstrates how to develop an advanced named pipe server that is capable of servicing 5 named pipe instances. The application is an echo server where data is received from a client and echoed back to the client. All the pipe instances are serviced using threads.

Compile:

cl -o Threads Threads.cpp

Command Line Options:

None

Source Code:

#include <windows.h>
#include <stdio.h>
#include <conio.h>
 
#define NUM_PIPES 5

DWORD WINAPI PipeInstanceProc(LPVOID lpParameter);

void main(void) {
  HANDLE ThreadHandle;
  INT i;
  DWORD ThreadId;

  for (i = 0; i < NUM_PIPES; i++) {
    // Create a thread to serve each pipe instance 
    if ((ThreadHandle = CreateThread(NULL, 0, PipeInstanceProc, NULL, 0, & ThreadId)) == NULL) {
      printf("CreateThread failed with error %\n", GetLastError());
      return;
    }
    CloseHandle(ThreadHandle);
  }
  printf("Press a key to stop the server\n");
  _getch();
}
// 
// Function: PipeInstanceProc 
// 
// Description: 
// This function handles the communication details of a single 
// named pipe instance. 
DWORD WINAPI PipeInstanceProc(LPVOID lpParameter) {
  HANDLE PipeHandle;
  DWORD BytesRead;
  DWORD BytesWritten;
  CHAR Buffer[256];
  if ((PipeHandle = CreateNamedPipe("\\\\.\\PIPE\\jim", PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE |
       PIPE_READMODE_BYTE, NUM_PIPES, 0, 0, 1000, NULL)) == INVALID_HANDLE_VALUE) {
    printf("CreateNamedPipe failed with error %d\n", GetLastError());
    return 0;
  }
  // Serve client connections forever 
  while (1) {
    if (ConnectNamedPipe(PipeHandle, NULL) == 0) {
      printf("ConnectNamedPipe failed with error %d\n", GetLastError());
      break;
    }
    // Read data from and echo data to the client until 
    // the client is ready to stop 
    while (ReadFile(PipeHandle, Buffer, sizeof(Buffer), & BytesRead, NULL) > 0) {
      printf("Echo %d bytes to client\n", BytesRead);

      if (WriteFile(PipeHandle, Buffer, BytesRead, &
          BytesWritten, NULL) == 0) {
        printf("WriteFile failed with error %d\n",
          GetLastError());
        break;
      }
    }

    if (DisconnectNamedPipe(PipeHandle) == 0) {
      printf("DisconnectNamedPipe failed with error %d\n",
        GetLastError());
      break;
    }
  }

  CloseHandle(PipeHandle);
  return 0;
}
Categories: C++ Source Code: C++ Programming Concepts
Tags: C++ ProgrammingSource CodeThreads
M. Saqib: Saqib is Master-level Senior Software Engineer with over 14 years of experience in designing and developing large-scale software and web applications. He has more than eight years experience of leading software development teams. Saqib provides consultancy to develop software systems and web services for Fortune 500 companies. He has hands-on experience in C/C++ Java, JavaScript, PHP and .NET Technologies. Saqib owns and write contents on mycplus.com since 2004.
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