network-light

A small, portable subset of the network package's socket API.

What this is

network-light implements a small subset of the socket functionality found in the network package: creating TCP/UDP sockets addressable via IPv4, connecting, binding, listening, accepting connections, and sending/receiving raw bytes, String, or ByteString. The API deliberately mirrors network's in spirit, so moving between the two should feel familiar.

It exists because MicroHs (mhs), a small Haskell compiler, cannot yet compile the full network package. network-light is implemented directly on top of the C socket()/connect()/send()/recv()/... calls via plain FFI imports (no C stubs) which keeps it simple enough to compile under both GHC and MicroHs from the same source. Until MicroHs can compile network in full, this package is the quickest way to get sockets working under both compilers.

This is not, and does not try to be, a replacement for network. It only implements what has been needed so far — Domain and SockOpt, for example, each model a handful of constructors, not the full POSIX surface.

Scope

• TCP (SOCK_STREAM) and UDP (SOCK_DGRAM) sockets over IPv4 (AF_INET)
• connect, bind, listen, accept, close
• Sending and receiving raw buffers, String, or ByteString, either "best effort" or looped until the full amount is sent/received
• A handful of socket options: SO_REUSEADDR, SO_DEBUG, SO_TYPE, and non-blocking mode
• Sockets are non-blocking by default and integrate correctly with both GHC's I/O manager and MicroHs's cooperative, green-thread concurrency
• Compiles under GHC and MicroHs, on Linux; a zephyr cabal flag selects the differing sockaddr_in layout needed for Zephyr RTOS embedded targets

If you need something this package doesn't have yet, such as IPv6, more socket options, Unix domain sockets, and so on, please fork it, add what you need, and open a pull request. Contributions are very welcome, as long as they keep to the existing style: plain FFI imports, no C stubs unless truly unavoidable, and code that compiles under both GHC and MicroHs.

Installation

cabal install network-light

or add it to your .cabal file:

build-depends: network-light

Example

module Main where

import System.Network

port :: Int
port = 4242

server :: IO ()
server = do
    serverFd <- socket AF_INET SOCK_STREAM
    setsocketopt serverFd SO_REUSEADDR 1
    bind serverFd (mkSockAddr port Nothing)
    listen serverFd 1

    (clientFd, clientAddr) <- accept serverFd
    putStrLn ("received connection from: " <> show clientAddr)

    msg <- recvString clientFd 100
    putStrLn msg
    _ <- sendString clientFd "Hello, client!"

    close clientFd
    close serverFd

client :: IO ()
client = do
    fd <- socket AF_INET SOCK_STREAM
    connect fd (mkSockAddr port (Just "127.0.0.1"))

    _ <- sendString fd "Hello, server!"
    reply <- recvString fd 100
    putStrLn reply

    close fd

-- Run `server` in one terminal and `client` in another; they will talk to each other.
main :: IO ()
main = server

Testing

The test suite lives under tests/ and is driven by make rather than cabal test, so that every test is built and run against both GHC and MicroHs from the same source:

cd tests
make test          # run every test under both mhs and ghc
make test HC=ghc   # GHC only
make test HC=mhs   # MicroHs only

License

Apache License 2.0. See LICENSE.