# nanomsg-haskell

This is a Haskell binding for the nanomsg library: <http://nanomsg.org/>.

There's support for [(evented)](http://hackage.haskell.org/packages/archive/base/latest/doc/html/Control-Concurrent.html#v:threadWaitRead) blocking send and recv, a non-blocking receive,
and for all the socket types and the functions you need to wire them up and
tear them down again.

Most socket options are available through accessor and mutator
functions. Sockets are typed, transports are not.


## Building

You would normally make sure the nanomsg library is on your system and then
install from Hackage, but can build from source following these steps:

  1. Build and install nanomsg (and zeromq, if you are building benchmarks)
  1. git clone https://github.com/ivarnymoen/nanomsg-haskell
  1. cd nanomsg-haskell && cabal sandbox init
  1. cabal install --dependencies-only [--enable-tests] [--enable-benchmarks]
  1. cabal configure [--enable-tests] [--enable-benchmarks]
  1. cabal build
  1. [cabal test]


## Usage

Simple pub/sub example:

Server:
```haskell
module Main where

import Nanomsg
import qualified Data.ByteString.Char8 as C
import Control.Monad (mapM_)
import Control.Concurrent (threadDelay)

main :: IO ()
main =
    withSocket Pub $ \s -> do
        _ <- bind s "tcp://*:5560"
        mapM_ (\num -> sendNumber s num) (cycle [1..1000000 :: Int])
    where
        sendNumber s number = do
            threadDelay 1000        -- let's conserve some cycles
            let numAsString = show number
            send s (C.pack numAsString)
```

Client:
```haskell
module Main where

import Nanomsg
import qualified Data.ByteString.Char8 as C
import Control.Monad (forever)

main :: IO ()
main =
    withSocket Sub $ \s -> do
        _ <- connect s "tcp://localhost:5560"
        subscribe s $ C.pack ""
        forever $ do
            msg <- recv s
            C.putStrLn msg
```

Nonblocking client:
```haskell
module Main where

import Nanomsg
import qualified Data.ByteString.Char8 as C
import Control.Monad (forever)
import Control.Concurrent (threadDelay)

main :: IO ()
main =
    withSocket Sub $ \s -> do
        _ <- connect s "tcp://localhost:5560"
        subscribe s $ C.pack ""
        forever $ do
            threadDelay 700           -- let's conserve some cycles
            msg <- recv' s
            C.putStrLn $ case msg of
                Nothing -> C.pack "No message"
                Just m  -> m
```