Thread: Pipes, inheritence and some newbie questions

Here's some code I'm working on. I'm a beginning programmer and i'm doing this as a (useful) experiment so that i can access my command prompt on my home machine when I'm away.

It was really an excuse to learn about pipes and inheritence etc.

Basically from what I can tell from learning about pipes, I've to pass the write-only handle of the pipe to the process, making its stdout send to the pipe.

The problem is that when I try to read from the anonymous pipe there's nothing to read. I don't know if this is the fault of the launched processes stdout setup or the fault of the pipe setup, though when I use WriteFile to write to the pipe I still can't read anything from it.

I see from the example in the SDK that they're using DuplicateHandle for some reason. I don't understand why at all.

Any help would be appreciated, I'm really stuck with this.

Code:

#include "stdafx.h"
#include "resource.h"
#include <windows.h>
#include <winsock2.h>

#define BUFFERSIZE 1024

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
	//Starting winsock	
	WSADATA test_wsa;
	int Sockreturn= WSAStartup(MAKEWORD(2,2),&test_wsa);
	if ( Sockreturn  != NO_ERROR ) return 1;

	//Making socket
	sockaddr_in test_sin;
	SOCKET test_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if ( test_socket == INVALID_SOCKET ) return 1;

	//Socket settings
	test_sin.sin_family = AF_INET;
	test_sin.sin_port = htons(808);
	test_sin.sin_addr.s_addr = inet_addr("127.0.0.1");

	//Connecting socket
	Sockreturn = connect(test_socket, (SOCKADDR *) &test_sin, sizeof(test_sin));
	if ( Sockreturn == SOCKET_ERROR ) return 1;

	//***************************************
	//makethepipe();
	HANDLE out_hread, out_hwrite;

	SECURITY_ATTRIBUTES sa;
	PROCESS_INFORMATION pi;
	STARTUPINFO si;

    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    ZeroMemory( &pi, sizeof(pi) );

	//Make pipe handle inheritable
	sa.bInheritHandle = TRUE;
	sa.lpSecurityDescriptor = NULL;
	sa.nLength = sizeof(SECURITY_ATTRIBUTES);

	//Make pipe
	CreatePipe(&out_hread,&out_hwrite,&sa,0);

	//Make stdout of cmd.exe write
	si.hStdOutput = out_hwrite;
	si.dwFlags = STARTF_USESTDHANDLES;

	int x = CreateProcess(NULL,"cmd.exe", NULL, NULL, TRUE, NULL, NULL, NULL, &si, &pi);

	char pipereadbuffer[BUFFERSIZE];
	DWORD pointlessvariable;

	while (1)
	{
		if(ReadFile(&out_hread,pipereadbuffer, 5, &pointlessvariable, NULL))
		{
			//Send some data (test purposes)
			send(test_socket, "test", 6, 0);
			Sleep(100);
			break;
		}
	}
	//***************************************

	return 1;
}

I am sure you would get an answer from the Windows programing board.

Try there - pete

Reposted - http://cboard.cprogramming.com/showthread.php?t=76360