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POC++: Implementing Named Pipes using the Win32 API
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  1. POC++: Implementing Named Pipes using the Win32 API
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    copied!<p>I'm trying to implement named pipes in C++, but either my reader isn't reading anything, or my writer isn't writing anything (or both). Here's my reader:</p> <pre><code>int main() { HANDLE pipe = CreateFile(GetPipeName(), GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); char data[1024]; DWORD numRead = 1; while (numRead &gt;= 0) { ReadFile(pipe, data, 1024, &amp;numRead, NULL); if (numRead &gt; 0) cout &lt;&lt; data; } return 0; } LPCWSTR GetPipeName() { return L"\\\\.\\pipe\\LogPipe"; } </code></pre> <p>And here's my writer:</p> <pre><code>int main() { HANDLE pipe = CreateFile(GetPipeName(), GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL); string message = "Hi"; WriteFile(pipe, message.c_str(), message.length() + 1, NULL, NULL); return 0; } LPCWSTR GetPipeName() { return L"\\\\.\\pipe\\LogPipe"; } </code></pre> <p>Does that look right? numRead in the reader is always 0, for some reason, and it reads nothing but 1024 -54's (some weird I character).</p> <p><strong>Solution:</strong></p> <p>Reader (Server):</p> <pre><code>while (true) { HANDLE pipe = CreateNamedPipe(GetPipeName(), PIPE_ACCESS_INBOUND | PIPE_ACCESS_OUTBOUND , PIPE_WAIT, 1, 1024, 1024, 120 * 1000, NULL); if (pipe == INVALID_HANDLE_VALUE) { cout &lt;&lt; "Error: " &lt;&lt; GetLastError(); } char data[1024]; DWORD numRead; ConnectNamedPipe(pipe, NULL); ReadFile(pipe, data, 1024, &amp;numRead, NULL); if (numRead &gt; 0) cout &lt;&lt; data &lt;&lt; endl; CloseHandle(pipe); } </code></pre> <p>Writer (client):</p> <pre><code>HANDLE pipe = CreateFile(GetPipeName(), GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL); if (pipe == INVALID_HANDLE_VALUE) { cout &lt;&lt; "Error: " &lt;&lt; GetLastError(); } string message = "Hi"; cout &lt;&lt; message.length(); DWORD numWritten; WriteFile(pipe, message.c_str(), message.length(), &amp;numWritten, NULL); return 0; </code></pre> <p>The server blocks until it gets a connected client, reads what the client writes, and then sets itself up for a new connection, ad infinitum. Thanks for the help, all!</p>
 

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