阻塞 pipe ConnectNamedPipe 不触发

Question

I want to do IPC using named pipes. Here is a test client/server that I attempted to make to communicate between two processes Client code:

#include <iostream>
#include <Windows.h>

int main()
{
    HANDLE pipe = CreateFileA("\\\\.\\pipe\\DokiDoki", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
    if (pipe != INVALID_HANDLE_VALUE) {
        char buffer[] = "DokiDoki from the other side :P";
        DWORD bytesWritten;
        WriteFile(pipe, static_cast<LPCVOID>(buffer), sizeof(buffer), &bytesWritten, NULL);
        std::cout << "Done!\n";
        CloseHandle(pipe);
    }
    else {
        std::cout << "Could not get a handle to the pipe!\n";
        return 1;
    }
    return 0;
}

Server code:

#include <iostream>
#include <array>
#include <Windows.h>

int main()
{
    char buffer[1024];
    HANDLE pipe = CreateNamedPipeA("\\\\.\\pipe\\DokiDoki", PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT, 1, sizeof(buffer), sizeof(buffer), NMPWAIT_USE_DEFAULT_WAIT, NULL);
    while (pipe != INVALID_HANDLE_VALUE) {
        if (!ConnectNamedPipe(pipe, NULL)) {
         //Setting a breakpoint here will never trigger.
            DWORD bytesRead = 0;    
            while (ReadFile(pipe, static_cast<LPVOID>(buffer), sizeof(buffer) - 1, &bytesRead, NULL)) {
                std::cout << buffer << std::endl;
            }
        }
        DisconnectNamedPipe(pipe);
    }
    return 0;
}

The program stops at ConnectNamedPipe and will not execute any other instructions, even when the client connects and writes to the pipe. WriteFile (on the client) returns true.

Answer 1

ConnectNamedPipe returns a nonzero value if it succeeds, which is why this wasn't working. Changing if (,ConnectNamedPipe(pipe, NULL)) to if (ConnectNamedPipe(pipe, NULL)) seems to work fine.