Error: ENOENT: no such file or directory, stat ‘/public/main.html’ at Error (native)

Since both the server and the index file are INSIDE the “public” directory, you can simply use :

res.sendfile('./main.html');

To answer the question in the comments : In Express 4.x, the sendfile method was replaced by the sendFile method (all lowercase -> camelCase). Probably just an oversight in early versions, that got fixed in the latter.