socket

Motivation

This library aims to expose a minimal and cross platform interface for POSIX compliant networking code.

Implementation Philosophy

• Every operation and every flag exposed should be supported with same semantics on every platform. If this cannot be guaranteed it should be supplied by another (extension) package.

• Absolutely no conditional exports.

• No #ifdef madness in the Haskell sources. The Haskell binding code uses the FFI to reference platform dependant C functions for each operation. If a platform is not POSIX compliant (i.e. Windows) equivalent functionality is implemented by using whatever the platform specific building blocks are.

Platform Support

Linux

Platform is fully supported. Each commit and release is automatically tested with Travis CI and several versions of GHC.

Windows

Fully supported on Windows7 (maybe Vista) or higher :-)

GHC's runtime system on Windows does not offer an event notification mechanism for sockets. The original network library suffers from this, too. For example, connection attempts are non-interruptible etc. The approach taken to circumvent this in this library is to poll the non-blocking sockets with increasing delay. This guarantees non-interruptability and fairness between different threads. It allows for decent throughput while also keeping CPU consumption on a moderate level if a socket has not seen events for a longer period of time (maximum of 1 second delay after 20 polling iterations). The only drawback is potentially reduced response time of your application. The good part: Heavy load (e.g. connection requests or incoming traffic) will reduce this problem. Eventually your accepting thread won't wait at all if there are several connection requests queued.

This workaround may be removed if someone is willing to sacrifice to improve the IO manager on Windows.

Each release is manually tested on a Windows 10 virtual machine with the latest Haskell Platform (64bit).

MacOS

Working, but not regularly tested.

Please report when it is no longer working on MacOS.

Dependencies

• base
• bytestring

Tests

The project uses tasty for testing.

There are two test suites: default and threaded which are using the same code. Only difference is that one is compiled against GHC's single threaded RTS and the other against the multi-threaded one. Run cabal test to run both in sequence.

In order to see details and colored output you may also want to try

ghc --make test/test.hs && ./test/test