On Tue, Jun 26, 2012 at 10:22 PM, Nicolas Trangez
Hello Cafe,
Some time ago I tried to implement a network service using iteratee (or enumerator, can't remember), but gave up in the end. More recently I wanted to create something similar (a similar protocol), but failed again.
So I'm looking for some example code or something similar (Google only helped slightly).
First of all, I don't care which API/library to use, I guess for my purpose all of enumerator, iteratee, iterIO, pipes, conduits,... are OK, so all feedback is welcome.
Here's the catch. Most examples out there implement some server which accepts a single client request, interprets it, creates a response, returns this, and closes the connection (or something alike, think HTTP).
The protocol I'd like to implement is different: it's long-running using repeated requests & responses on a single client connection. Basically, a client connects and sends some data to the server (where the length of this data is encoded in the header). Now the server reads & parses this (binary) data, sets up some initial state for this client connection (e.g. opening a file handle), and returns a reply. Now the client can send another request, server parses/interprets it using the connection state, sends a reply, and so on.
Might sound easy (and actually it's pretty easy in most other languages I know, including an OCaml implementation), yet I fail to figure out how to get this done using some enumerator-style library.
Thanks for any help, I'll most likely write up something if I get things working for future reference.
Nicolas
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I've run into those kinds of problems in the past as well. In general, interleaving of data streams can be difficult with enumerator. That's the reason I added connect-and-resume to conduit. I use the technique in warp[1], which in fact *does* support multiple request/response pairs due to connection keep-alive. But the code base isn't the easiest introduction to the technique. If there's interest, I'll try to put together a blog post on using connect-and-resume to solve this kind of problem. Michael [1] https://github.com/yesodweb/wai/blob/beta/warp/Network/Wai/Handler/Warp.hs#L...